Hello everyone!

So I've been playing D&D for a while now and decided to create my own campaign, and I really want to try and avoid cliches as much as possible. The overall plot is basically that there is a god that was sealed in a mountain by another god a long time ago, and as the enchantment that holds the evil god in the mountain is fading, many of his followers are rising up to attempt to free him. I understand that the plot itself if pretty tired, but I think that if the in between quests leading up to it are different that it wont matter as much. 

I have been developing an arc for the story for a while, it involves a necromancer who is one of the leaders of the order attempting to release the evil god. Basically, he goes from town to town, summoning shadows, the shadows multiply enough and it ends up being like a plague of sorts. The necromancer collects the shadows and uses the stored souls of the people trapped inside the shadow as energy to fuel the spell that will release the god from his prison if the players do not intervene. 

This is the most developed storyline I have so far, let me know what you guys think of it, or if you have any ideas yourself!

As long as you like, go ahead with your story.

My suggestion is just this: make sure have a solid adventure hook for the players.

The best advice I can give you is this: Play the NPCs, not the story.
Don't get too attached to the events you planned, enter in your NPCs mind and play them. And if they end up killed before you planned, don't sweat over it, let your PCs get the win, and make them discover something (a letter, a sygyl, something) hinting of another NPC (bigger and badder), this way a new arc will begin. Arcs can be cut short or can be prolongued. 
In short, don't focus too much on the arcs and the story, focus on the NPCs and play them out accordingly.

Another quick tip: At the end of each session, when all the players are gone, take half an hour and assess how the NPCs would respond to the events that just happened in the session. During the following week, prepare a few things to show your PCs the world is responding to their actions.

EDIT:
Examples for the quick tip:
The players decided to make a short rest after a battle while something bad is about to happen? Make it happen while they are in the short rest. Or maybe they find corpses and the enemy gone when they get to where they were going.

The players didn't chase a fleeing orc? What will the orc do? Is he going to call for help? Or is he going to alarm his partners and they may prepare an ambush? Make the players recognize the orc if they see him again.

The players mistreated someone in town? Is she vengeful? What may she do to get her payback?

Every action have the potential to be meaningful. Not ALL actions HAVE to be meaningful, but most of them can be.

Create a persistent world, so whatever your adventurers do or decide to go have it planned out...kind of. I use a large world map, I personally don't have eveyr single town and city and piece of terrain described but I do it as I go. As far as character hooks go base it on the class/race thing. An Elf Wizard might have a vision of doom and chaos on the cosmic plan, a Cleric hears an answer to a prayer from his deity, a Bard hears an outlandish story, a Fighter is pursuing a comrade in arms, a Paladin is sent by his Order, a Rogue is after a lady he had a fling with (who is involved with said cult but he doesn't know), Warlock's patron wants her to pursue its wishes, a sorcerer seeks the secrets of some power...

Use that as kind of a baseline for why the characters on the adventure, I've found the whole " You've all been hired on as mercenaries" is a kind of cliché, quickly thrown together thing that doesn't provide much meat to the story.

EDIT: DO NOT FUNNEL your players, if you force them in one direction it will suck. Let them decide where to go, and create what you need to continue the story along the way.

Not sure if you were or not, but don't plan on your players fighting the all-powerful deity. Not because it wouldn't be an awesome fight, but because (chances are) they will never reach the level you want them to in order to fight said god. Whenever I write a campaign, I usually figure my PCs will max out at 10 (if I'm lucky), so set up the big bad to be around that level.

My suggestion is making the Necromancer encounter a level 9-10 encounter. And then RIGHT after he's defeated, the god rises in the form of its avatar (not the full power of the god, mind you). Why did he still make it here? Maybe the Necromancer's ritual was a success and the god has to gradually acquire its power back now that it's on this plane. Maybe it wasn't successful, but the god was able to squeeze enough of its power through to progress its evil ways. Either way, this is the Big Bad Evil Guy (BBEG) encounter with the god boss (the one I told you before not to do), but at a much lower level than what would be required if he was at full power. If your campaign seems like it's good to end here, make this the last encounter. If you feel your campaign can continue to grow from this point, maybe the BBEG desires more power before enacting his plan. Maybe he wants to free his powerful and loyal lieutenants before marching forth to challenge the other gods. Or maybe, during the fight with the necromancer, the PCs learn of the BBEG's former enemy that banished him and they set off to find the one being that would be able to fight him (and the BBEG has to discover and then send his minions to each of the ritual sites to attempt to stop the PCs). 

Don't forget, other things should be going on in your world that aren't a part of the god's plan. Not EVERY bad guy has to be associated with the resurrection of the god(s) (though maybe their plans started BECAUSE of the rituals).

For example: in my campaign the BBEG is an Illithid Elder Brain who was slumbering deep within the earth (imagine Mother Brain from Metroid or the Cthulhu-type mythos). The reason the elder brain awakens is because a certain clan of drow elves are attempting a ritual to block out the Sun so that they can rise above the Underdark to take over the surface world. The ritual to do so has been lost for forever, is roughly translated, and isn't quite a complete copy, so the drow spellcasters are so far unsuccessful. However, their attempts to complete said ritual has been causing earthquakes all around the world; one of which unknowingly caused the elder brain to awaken. As a result of the elder brain awakening, the surrounding towns and even the wild monsters begin showing signs of madness and/or aggressive behavior. 

So here we have one force of evil attempting to do something that has nothing to do with the other; however, the actions of one evil force unknowingly caused the BBEG to awaken. And other, normally bad but now downright evil, forces are being influenced (but not necessarily controlled) by the BBEG. 

Thank you guys for all of the comments, I could really use all of the information I can get. I agree about NPC development, that's what I was most interested in anyways, I have a lot of them fleshed out and ready to go, trying not to get too attached to them. 

I'm definitely not planning on the players fighting the god as an end boss unless they do progress to level 17+. Unless I actually have another god come and help them with the encounter when they're at a lower level. What do you guys think about that?

I would say don't worry about using cliches as long as you make them your own, especially if you're DMing for players who aren't used to playing said cliches. I took some inspiration from Dark Souls in my first campaign, but mixed/matched some of the ideas together to create new individuals, but then I gave said individuals their own personallities (sometimes creating them on the fly when characters would ask about them). Like others have said, REACT to your players, don't PLAN for them. You'll probably be surprised that it can be even more fun when that happens. :P

But yeah, cliches can be your best friend if you're not great at creating unique ideas. Even when naming towns people try to come up with really complex or convoluted names, but stuff like WoW has simple names like "Goldshire" and "Darkshire," but people remember those so if it's not broke don't fix it. As long as your players can get into it, it doesn't matter if it's hokey or overused. Just don't make it too hokey  (The Dwarf city of Dwarfton, the Elf city of Elvenvale) if your players don't like that.

TL;DR - Don't be afraid to just try whatever works for you, as long as you're making it your own in some form or another.

As was said before, definitely don't get attached to anything in your story. Let it unfold organically, with your players having as much a hand in telling it as you. Be flexible, and try to roll with whatever happens. That's what I've found works best for me as a DM

Quote from Yungbob56 >>

I'm definitely not planning on the players fighting the god as an end boss unless they do progress to level 17+. Unless I actually have another god come and help them with the encounter when they're at a lower level. What do you guys think about that?