If you're interested specifically in WR or any other major FPS game like it, start off with C++. Pretty much any major site out there will help you grasp the basics of the language. Ideally you'll want to expand your knowledge to encompass ASM and stuff like reversing and general hacking (just search for tuts online or ask some of the guys in the programming section). Personally I recommend you check Lena's tuts on reverse engineering - great stuff to get you started. Finally if you'll want to play around with visual hacks D3D hacking and general use is a must-know, so look into that too