TekAngel - since I know that Evil Chris can't admit that he fucked up, I'll get this back on topic
Assuming the program offers all 4, use them in this order:
1 - PPS with cheap trial
2 - Revshare with no trial
3 - PPS with no trial
4 - Revshare with cheap trial
That's not to say there are not exceptions - say a sponsor offers 2 & 3 (this is very common) After an amount of hits or a time frames has passed, you look at your stats & see that the the average Revshare signup is making you less than a PPS, then switch the codes.
There's other scenario's, but that list is a good guide