Welcome to LQ and - that's the spirit!
The best way to start this is to learn to compile the kernel. read the help files in the source code and read the kernel forums and mailing lists. Just read them, get a feel for the discussions. Kernel-org has suggestions on where to start.
To participate in such high-powered cicles though - really really really read the advice link in my sig. I mean it.
Find a part of the kernel that interests you and start playing with the code in that area. Work out what does what and why things are set up the way they are. When you think you are getting the hang of it, start talking to other people working on it. Back up what you say with code. Listen to them about what needs doing.
The open-source project you can contribute to is the kernel project
Usually, you pick a driver though, especially if you happen to have poorly or non-supported hardware yourself. Look for drivers you care about and check out the project pages for a todo list.
Good luck and happy hacking.