By far THE SINGLE GREATEST MISTAKE new game developers make is taking too long to make a game.
It's a very common and depressing story: some guy has an idea for a game, begins a journey to create their "passion project," 3 years later if they did manage to finish their game, it got only 5 people to wishlist it on Steam, if any at all, and their post-mortem will say they should have "done more marketing" or something like that.
This just sounds absurd to me.
There are Three Types of Game Developers
1: game developers who never made a game.
2: game developers who made one game.
3: game developers who made two or more games.
Don't be ashamed of making terrible, buggy, very short games that look unfinished.
Do you know what you call someone that has made several generic browser games that you can actually play? A game developer with lots of experience.
Don't spend 2 years making a single game, creating a company to release it, making 3 sales, and then filling for bankruptcy because only now you realize how much money you can earn making indie games.
Make Games to Flop
3 months or 3 years, your first game is going to flop anyway, so why waste so much time making it?
People have no idea how hard it is to make a game. They will not appreciate your hard work. That means you don't need to work hard because it won't matter anyway.
If you use pre-made assets, it's going to look like you're an amateur.
If you make your own assets, it's ALSO going to look like you're amateur, but now you'll have wasted a dozen times the effort making it!
You really don't want to waste any money making your first game. You have higher chances of losing money than of making money.
Budget for Your Incompetence
Imagine that you have 1 thousand dollars. You want to build a new room on your house. That project is going to cost you 5 thousand dollars.
What normal, sane people do in situations like these is they say: well, I can't build this, because I don't have the money I need for it.
What you DO NOT say is: I'll just start building it, and then I guess maybe I'll find the rest of the money off the ground or something.
That's just insanity! That's not how it works. You can't start a project without the things you need to complete the project!
Can you program? Can you draw? Can you model? Can you compose music? Can you record sound effects? Can you voice act? Can you write? Can you design? Can you market? Do you have the time to play test and to grow a social media following?
What CAN'T you do?
The things you can do, you can just do them when you need to do them, but the things that you can't do are going to get done how? These things still need to be done if you need a game.
Don't wait until you need the artwork or the music to think about what are you going to do about the artwork or the music. A game is the whole interactive multimedia experience. When you can create any sound, you are free to do whatever, but if you are limited to using only assets you can find for free on the Internet, for example, then you should change THE REST OF THE GAME to match what you have available in order to create a cohesive experience.
You want to make a WWII themed SHMUP but you can only find spaceship sprites for free? I guess you're making a space SHMUP now. You really want to make a 1942 clone? I guess you can find one airplane sprite and just put it in space. No bullet sprites, only beam sprites? The airplane shoots beams. This is already sounding way more epic than anything you would come up with.
If you can't make a game with free assets, you can not make a game with a hired artist or partner either. The ability to compromise is the most important skill necessary to actually make things instead of just talking about making them.
Make a list of your competencies and incompetencies and come up with a plan right now to figure out how you're going to cover for that, because it's just not realistic for you to learn 5 different careers just to make one game.
Who knows, maybe when you take a look at what kind of graphics and sounds you can get for free, you'll feel that vast ambiguity of design decisions that you would have disappear, since now you HAVE to use one of these graphics and sounds, and nothing else, your game HAS to be in a certain way to match. There isn't much to decide or wonder about anymore. It's a clear, straight path from start to finish.
Join a Jam
If you're interested in making games fast, be sure to participate in the Ludum Dare [ludumdare.com] one of these days, a game jam about making a game in just 2 days. A single weekend.
If you can't make a game in 2 days, you sure can't make a game in 2 years either. Come on, just make tic-tac-toe or something. That's not hard.