How do you do it? Do you think certain archetypes? Do you emulate a certain person or character?

I'm interested in seeing how others integrate the roll playing with the role playing originally.

When creating a character I of course take into account the setting, the DM's guidelines, My roll for stats (Ignore this when playing standard point array) and what the rest of the party is feeling but I like to start by taking the idea of the character and working backwards from there to fit the mechanics to the character. I like to start with some of the voice or thoughts of the character and let that inform the game mechanics. I also vary it depending on the character I'm working on, when being "inspired" by a real person I try to emulate the essence of them and turn that up. What are some of the things y'all do?

Your background can give you random tables in which to roll around 4 or 5 different one-liners. These can be used as a basis on which to build a personality.

I don't use archetypes really, nor people, nor characters out of fiction.  I usually have little or no knowledge of the setting.  I make most of my character to be pretty much by-the-rules setting neutral.  Once I get a chance to play, I talk to the DM about what they want to see and adjust from there.

I generally start by looking at the class.  I look at Warlock, for example, and ponder.  What would a good aligned Warlock be like?  Do I want to lean into the stereotype and play an Aasimar, or subvert it by playing a good aligned Tiefling?  Maybe another race entirely would be better?  As I'm building the character in the Character Builder tool, I use Point Buy to generate the scores, and I'll be thinking about which background to use and what skills would make sense, what languages they might learn, what gear they might be able to pick up, and so on.  Then I figure out what my backstory is and how I want to roleplay based on it.

Answer some questions about your character's origin and motivation. There are plenty of questions, but here are a few:

Why am I a (Class/Background)?

What is my motivation as an adventurer?

Why have I elected to stick with the party?

Another great roleplaying tool is quirks. Whether it be a funny way of speaking, colorful Kobold scales, or a tendency towards pyromaniacy, quirks give life and character to roleplaying.

I have so many different characters already built over the years that I've played the game; it's really just a matter of deciding which of them fit/ which ones I want to play in a campaign or one shot. 

In terms of informing my role play, I love having a low stat and building traits around that. It's easy to do and makes for much more flavorful characters in my opinion.

Try to play 20 questions with your character.

Come up with a question that would make sense to ask your character, and then try to answer it in character.  Repeat 19 more times (at least)

This is a great way to flesh out a character concept and the more you do it the easier it gets.  
Questions can be things like 'What was life like growing up?', 'Who do you see as your mentor?', 'What is your driving motivation in the world?', etc.

Also keep in mind, adventuring is dangerous work, normal people don't do it.  What makes your character abnormal enough to consider this line of work?  One thing I used to do was I had a textbook on abnormal psychology and as a GM I would have every player pick a disorder for their character.  If they chose a particularly debilitating one I would give them some bonus to counteract it to some degree and I would award extra XP for roleplaying it well.  Added a LOT of flavor to campaigns.

My primary concern is always about synergy. I don't want to play a character who will shun or be shunned by the other PC's. I try to make my character have enough good points to counterbalance the bad, and so will likely be accepted even if they are a little flawed. I've tried using a character who considered anyone not an elf contemptible, and was an insufferable know-it-all, and they got on with the non-elf party as well as you can imagine, so I dropped them. Their character made perfect sense, but not for adventuring in a group.

So, number 1 is "why are they with the party / would they stick with the party / would the party let them". Number 2 is to make them interesting - perhaps a troubled past which resurfaces, such as a blind refusal to let anyone ever be tortured. Perhaps the rest of the party notice this, and if they ever ask, backstory comes out with some tragedy that nobody else knew, like seeing their significant other tortured and vowing never to let it happen again.

So, if you want a character to behave in a certain way (EG always being the joker of the group) then that needs t ogo into the backstory - why do they joke? are they just a jovial person? are they hiding a trauma with every quip? Were they mentally conditioned by overbearing yet concerned parents to turn every murder-based thought into a joke so that their little boy doesn't grow up to be a murderhobo? Are they cursed by the gods to see the funny side of things, no matter how inappropriate, after a youthful gatecrashing of a funeral which they laughed at?

As soon as you give the character a reason to behave like you want them to, it becomes so much easier to roleplay them authentically.

I'm all over the place. Sometimes the character is based off artwork or a particular mini. Sometimes the Background characteristics inspire me. Sometimes it comes from the setting or another player's character. I try to stay open to changes as I build the character, and I'll often end with a different concept than I began with.

My process is to spend time thinking about a character concept. Sometimes i get a spark from a class/race combination and build out the concept from there, sometimes the other way. All the while coalescing the essence/spirit/soul of the character, how they think, morals, triggers, values, what and who they care about, strengths, weaknesses. Once i "know" all this, the role play is pretty straightforward.

I play that character. I know what they will say and how they will say it. How they will react to a situation, whether its good for me the player, or bad for them from a meta standpoint. If my paladin sees injustice, she will respond, the devil be damned! My sorcerer will likely be indifferent unless it may benefit him.  

I note ideas about dialogue, such as catch phrases, or snippets of dialogue. I review them from time to time, not to memorize them for recitation, but to get into the character. I think about how they will react to other characters in the party, as well as NPCs in potential situations. My paladin sometimes swears like a sailor when fighting fiends without realizing it. When she does, she's embarrassed afterward and apologizes. My Ranger wouldn't utter a word unless to quietly exchange tactically information. Afterward, he might say nothing, or make some profound pronouncement about the encounter.

Its a role-playing game. Role play!

I like to come up with one core concept that can be spelled out in a word, a few words, or a short phrase or two.  Sometimes I'll mix an match, 'mad libs' stype. 

So I had a favorite Star Wars character.  "Action Hero" was the main concept.  Jumps, flips, stunts etc.  But I wanted to mix it up so I added a "Clueless".  And viola my Dante was born.  He was fantastic at swinging a light sabre (once obtained), pretty darn hot with a blaster, able to leap small buildings in 2-3 bounds, you get the idea.  But was a complete novice about the galactic civilizations.  Grew up on a junk planet the Empire had been using for years.  Social interactions?  Trust everyone!  Why wouldn't you... what is a lie?  Why would someone do this lie thing?  Notice someone sneaking.  Nope.  

Another was based on an old text game.  It had a helper robot who liked to... "Help".  So the concept was "Dedicated Helper".   Made a Warforged Bard named FLOYD (Yes all caps) and really really reeeeeeaaaallly like to help people.  Not totally subservient, but would just love to make people happy and help them.  Buff spells, heals, cooking, you name it.  And he was really helpful to NPCs, even the not-so-nice-ones (at least until they showed they were bad.  The voice schtick too, always talking in a little-to-happy voice, at all times.  

Last example was a human fighter who wanted to be 'The Best'.  Roleplayed bravado to a fault.  Accepted pretty much any challenge.  Rushed into combat.  Odds?  I don't care about the odds.  No self preservation at all.  

Of course the character traits for backgrounds are all fun too, and you can mix and match.  I know a few DMs who have dual backgrounds (ie kid growing up, and one for more adult).  And Xanthar's Guide has some good background rolls to.

 About fifteen years ago, as my autoimmune disorders were beginning to get really bad, falling asleep became hard for me, because I was in so much pain.  I began making up stories in my head as a method of relaxing, which of course heavily involved character creation; it became a habit, to the point that now I can no longer fall asleep without it!  So when I started playing D&D a few years ago, character creation came naturally to me.

I either start by building the personality of the character I want, and then use that personality to build a backstory, or build a backstory, and then develop a personality out of that.  I always build casters, because that’s what I enjoy role- and roll-playing.  Beyond that, I put together a few phrases that encapsulate my character’s worldview.  “I always feel compelled to play devil’s advocate.”  “Art is the purest form of worship.”  “I can’t help but try to comfort any creature I meet who seems to be suffering.”. “I can’t resist an opportunity to play the mysterious sage.”  And so on.

I also use physical characteristics to hint at personality traits: a High Elf wizard who wears nothing but purple silk refuses to perform manual labor; a Tiefling sorcerer who struggles to control her fire magic has burn scars; the paranoid animistic Dryad druid refuses to wear anything but hides of dead foes, or use any weapons unless made from the bones of her kills, for fear of offending the spirits of the plants used to make clothing and weapons.

Possibly the most important thing about my characters is that they are motivated by more than just hopes and/or fears.  I try to give each one a consistent moral code by which to live and make decisions.  This helps me avoid making them one-dimensional, single-minded robots who can’t learn or grow.

Oddly enough, stats are almost the least important aspect of these characters.  I always make sure I have a reason for the highest stat and the lowest stat (eg. the Scourge Aasimar cleric has a low strength score because her Radiant Consumption feature burns away at her musculature), but otherwise, thay’re just numbers.  Needed to play the game, but not the defining aspects of these imaginary friends.