So I assume that you know java somewhat. If so, I'd say the best thing to do is to look at the RCX tutorial then and the samples. If there is any difference between the RCX and NXT notation, you can just check the NXT API.
Actually... I wrote a tutorial for someone at my school... I'll see if i can dig it up.
FOUND IT! it doubles as an intro to java too so if you happen to be a little rusty in that, it will get you up to speed.