I'm a noob DM (as well as a noob to DND as a whole) and my Party is understanding and forgiving of my noobness and mistakes I make. Something I am still struggling with is knowing which rolls to make at which time, and knowing what to calculate against. I have an affinity for doing research but cannot find a STUPID simple answer on the internet. I've asked various persons, but maybe my brain is just constructed differently. Is there a flowchart or a plain and simple step by step diagram that breaks it down to Player does XYZ, then DM does XYZ...the die or dice used for both...the DM calculates ABC for_____....and so forth. 

Quote from EmeryldRaine >>

I'm a noob DM (as well as a noob to DND as a whole) and my Party is understanding and forgiving of my noobness and mistakes I make. Something I am still struggling with is knowing which rolls to make at which time, and knowing what to calculate against. I have an affinity for doing research but cannot find a STUPID simple answer on the internet. I've asked various persons, but maybe my brain is just constructed differently. Is there a flowchart or a plain and simple step by step diagram that breaks it down to Player does XYZ, then DM does XYZ...the die or dice used for both...the DM calculates ABC for_____....and so forth. 

 Sorry to inform you but the answer is no.  It's your decisions and you judgement calls that guide when to roll a die or not. 

I would suggest trying to study some of the published campaigns till you get the feel of how it goes and get comfortable with the material. 

The dmg and the player's manual are the bulk of your rules and when things apply. The dmg is kind of less so. I think you really only need chapter 9 and a few others to get rules. The rest is world building. 

I advise you to keep a character sheet (blank or otherwise) handy when DMing. I find it help a lot to have a list of skills to hand t oquickly glance through and pick an appropriate one.

Also worth asking players to clarify what they want to achieve, it can make a huge difference:

"I want to check the stone path..."

...for tracks: Survival.
...for who might have made it: History.
...for if it was made with magic: Arcana.
...for if there are signs of a struggle: Investigation.
...for if they are local stones: Nature.

etc.. It's much easier to pick a skill if you know what they are looking for, or looking to do.

In a very general sense, the D&D gameplay loop is Declare, Determine, Describe.

• The player Declares an action their character is taking.
• The DM Determines the outcome of the action - this may or may not require a roll.
• The DM Describes the outcome of the action.

This is gone through in much more depth by angrygm here - https://theangrygm.com/declare-determine-describe/  He's a bit of an acquired taste, but his articles are solid.

Now it sounds like you want something a little more in-depth, like when to roll and when it's not necessary, and what to roll when. That is largely just going to take some time getting familiar with the most common options and getting a feel for how to handle the uncommon situations. It may help to go over Chapter 8 of the DMG, which talks about the role of dice and goes over the various ability checks. The PHB also gives you a description of each skill and what proficiency in said skill can help a character accomplish.

To break down Determine a bit more, I'd go through this process:

• "How do you want to do that?" - The player can't just say "I want to get a lower price from the shopkeeper." Ask them how - by getting all buddy-buddy with him? By threatening him? By saying you saw the same item for half price down the street? You need context for the next part.
• Does it really need a roll? - If something is very easy or impossible, it's ok to say, "Ok you do that" or, "You can't do that." You may also skip rolls when failure isn't interesting and there's no reason the character couldn't just try again. This can also apply if players are spending a resource like a spell to do something. Often if my players use a spell or class feature I will just let it auto-succeed because they are doing something they are supposed to be good at. If no roll is needed, you can skip straight to Describe.
• If it needs a roll, what to roll? - This is where the context helps. Buddy-buddy? That's Persuasion. Threat? That's Intimidation. Get to know the skills, and you can just pick the one that feels like it fits with the declared action. If it's not clear, feel free to go back to "how do you want to do that?" Sometimes pointing out what a character is trained in can help a player think a bit more critically about how their character would approach a problem - I would encourage talking about this early on with newer players even if it breaks immersion a bit. Most of the time an ability check with an appropriate skill is the answer here.
• How hard is it? - Back to Chapter 8 of the DMG, it has a very general chart for determining the DC of a check based on how difficult you think it is. This part of the game is very fuzzy and I wouldn't worry too much about it, just ballpark it for now. As you play you will get a better grasp of how it all works and will be able to just come up with DCs on the fly. Note that this can result in building your world out on the fly - if a player intimidates the shopkeeper, you need to decide how easily intimidated the shopkeeper is. Maybe you decide he's a grizzled war vet who isn't easily cowed. Or maybe he's a pampered merchant's son who folds like wet tissue paper. Make it up as you go, but write it down because it may be relevant later. This can be intimidating, but it's actually a fun way to grow your world and get into your own story. 
• Call for the roll - Have the player roll the appropriate ability check. Eventually you may want to do some of these without them seeing the outcome - a lot of people like to do this with skills like Insight where a bad roll might result in a missed cue or misinterpretation of something, but when starting out I'd recommend just rolling out in the open.

I make it as simple as I can: is it a task that most individuals would be able to carry out without effort?

If yes, then no check is needed.

If no, then a check is needed.

For example, if the task is opening a door with no lock - no check is needed. If the task is picking the lock on a locked door - a check is needed.

One requires expertise, the other doesn't. 

If you're desperate for a flowchart though there is one here: (2) Creating a Newbies Flow Diagram for taking actions in D&D. What would you change or add? [OC] : DnD (reddit.com)

"cannot find a stupid simple answer" cause it doesn't exist. DMing is part experiment part art part gut feeling. Page 174 of the players handbook is where you should start though. The difficulty classes list can be applied to about anything. You as a DM decide where something falls on that list. 

Could you give examples of situations where you were at a loss on how to adjudicate the outcome? 

It might not be as complex as XYZ but as simply as saying they said a lot of words to describe "breaking something". Breaking = an Athletics check. 

I know this may get burried as there is a lot of replies but I have taught many people how to play and explained so much that I wanted to jump in. Breaking it down into categories really helps.

-Strength rolls are anything that's gonna make you sweat, holding something for a long time, lifting heavy things, wrestling, etc. That is why Athletics is the only one that falls under this category. 

-Dexterity rolls is moving with purpose. Rolling over a table, climbing a sheer wall, running across walls, etc. Acrobatics fits into this category for obvious reasons. Stealth and sleight of hand are both moving with purpose in different ways. Stealth to keep quiet, and slight of hand for when you need to use your hands (lots of DMs use slight of hand for stealing and lockpicking only. However tying knots, moving levers carefully, and balancing can all be Sleight of Hand as well.)

-Constitution is your inner strength and so it is used when trying to save from poisons, from being crushed, or anything that physically affects the body. No skills use Con because you can't outwardly use an inward force!

-intelligence is knowledge. It is the innate remembering of specific pieces of information. When going through the skill list, a good rule of thumb is to add "the history of" before any intelligence roll. What is a religion check? "The history of religion." It can extend to modern history but it is anything that can be known about that specific skill. The higher the role, the more information they can remember.

-wisdom is street smarts. Or better yet, the outpouring of knowledge in specific circumstances. Most wisdom checks are studying a scene and seeing how you can work within it. Animal handling-how can I use this animal to my advantage. Insight-how can I use the movements, facial ticks, and vocal intonation of this person, place, or thing to my advantage (insight is very useful for more than just seeing if an opponent is lying!!!). Medicine-how can I use medicinal supplies and knowledge to help in the situation. Perception- how can I look around and see what I can use to my advantage. And survival-How can I use my cub scouts knowledge to help in this situation. 

-finally, Charisma is the act of using your body, voice, and charm to convince. Convince someone in a deceptive, intimidating, or persuasive way.

With this knowledge it makes it a bit easier to recognize when your players are going to need to use the skills. Most of the time, depending on players, there won't be many roles when moving between scenes, but many in dungeon and closed in spaces. If you have any questions DM me! Love chatting D&D

Thank yoo so much!