http://unity3d.com/learn/tutorials/topics/developer-advice

Watch those videos.

Then you should either decide to use an existing engine or pick up a few libraries in you chosen language as your tool set. Then start playing around and try to make some very basic stuff like pong, breakout, ect... Good luck and don't forget that you will probably end up reading a ton of books/tutorials!

Above all else make sure the projects you pick to learn from are fun and interesting to you.

Be careful. Making a game in C++ is definitely a fun challenge (and sometimes fustrating), but you must make sure that you have experience in easier methods, such as using GameMaker, or Unity. Making a game in C++ is pretty much the second hardest way to make a game/game engine, aside from making the whole thing in assembly. You will need a lot of experience to aid you, so that you do not feel like you are overwhelmed.

I'd highly recommend starting with GameMaker, Flash, or any 2D game making software, and then move up to Unity, and then the C++ stuff if you are ready for it.

"Aside from this, what other things do I need to know in order to make a game?"

Lots of things

-A lot of 3d math, preferably Linear Algebra and Trigonometry. You may not need to know any Calculus, except if you are doing something extremely complex and unique involving 3d functions and rates of change. Linear Algebra is very important, as it is used to transform(translate, scale, and rotate) objects, as well as graphical effects like shadow mapping.

-You need to know where all the tutorials are at. OpenGL-Tutorial.org, Rastertek.com, etc.

-You need to know how to load files as fast as possible. Loading in video games is always too slow, so the faster the better. Get used to using a lot of binary files, and loading a lot of contiguous data.

-Know which libraries to use. This is very important, because different libraries can support different Operating Systems, and may or may not be up to date, or as fast as others. AFAIK, there are about 20+ different rendering libraries out there.

-Know how to compile a library. I wrote a topic on that here: http://www.gamedev.net/topic/663810-how-to-compile-libraries-for-c-mingw-with-msys-on-windows-for-indie-game-developers/

What kind of 3d game are you looking to make?

When you say from scratch do you want to do absolutely everything yourself or will you use libraries for collision/physics...etc?

Do you have an idea for what you want to do about content ie 3d models?

Infinisearch, I've been looking to make a simulation game.

An RTS or something else? This will help people give you a list of what you need to learn.

And I want to use libraries so I don't have to write everything myself

That's good, it will allow you to approach game programming from the top down without worrying about the details, at least initially. Look into a physics library for collision detection (IIRC you don't actually need to use the physics), a sound library for loading and playing sounds, and potentially more.

And what do you mean what I want to do about content?

As you might imagine getting content for your project can be one of the hardest thing for a programmer, so have you looked into getting content? Have you looked into what format your (lets say) 3d models will be in? This way you can find a library or start coding a loader for them yourself.