For real-time games written in OO style, you'll have a gameloop which updates all the parts of your system. You'll divide your code into modules for rendering, audio, input, resource loading/management, gameplay, etc. and use a prioritized task list for this.
Gameplay will be your glue - the rest of the modules should be as independent from the others as possible. Each module will consist of dozens of classes. Each class should favour aggregation over inheritance, private over protected, protected over public. Each class should have one purpose, and it'd be good if you can separate your interface from your implementation (using abstract base classes, pimpl idiom, etc.). Use RAII when it makes sense (see Boost smart pointers). These are the fundamentals of most design patterns, and it'd be a good exercise to go over them so you don't reinvent the wheel.
A good way to manage content to your game is to use a component based architecture. First paper I know of describing this is from Dungeon Siege (I think this has a link to it:
http://www.purplepwny.com/blog/?p=215). Radical Entertainment switched to this system after Hulk for their new game called Prototype - they had a talk about it at GDC Canada this year. We also use it here at Next Level Games. If your game is really simple, don't bother. Just do whatever is simplest to get your content in the game.
If you're just starting out, rely on the C++ Standard Library. It's good enough for pretty much anything you'll be doing. Another good habit to get into is to use Boost, especially their smart pointers. Makes life easier as a beginner. If you run into performance issues, you can always go to a hand written solution.
Most important of all - SCOPE YOUR PROJECT. Keep it simple or you'll never finish it. Have a vision for it and stick to it so you don't go off on coding tangents. Profile your code before you optimize. Have a plan based on milestones with clear goals for each.
If you're stuck, don't beat your head against a wall. Go to
www.gamedev.org, do a search, and ask for help if you need to!
~Owen