1) setup everything so you can build tremulous(version of your choice)
1.1) build it
1.2) test it
2) modify tremulous.h
2.1) build it
2.2) test it
3) start changing other files in the game directory
3.1) ...
3.2) ...
4) call it [insert your name here]'s game.qvm
4.1) release it
5) ....
6) PROFIT