This is what I've learned from my use of p-valves:
1) Rochester Widebands *never* blow off.
2) After several days of diving, the glue tends to build up and you can lose skin taking the catheters off. Scrub *well* after removing it and the next one will be much easier. If you're enjoying the scrubbing, you're doing it wrong.
3) Trim the grass.. you don't need to look like a porn star but hairs that find themselves in the wrong place can really tweak.
4) Cut a bit off the tip of the catheter to avoid kinks. Trim enough so that the nipple on the p-valve goes just past the tip of the catheter.
5) If it's hot outside, put the catheter on before going to the dive site. Sweat keeps it from staying on.
6) If it's cold outside, put the cathetar on before going to the dive site. If your turtle has run back into his shell, the cathetar won't have as much surface area to adhere to.
7) Give it a test go before suiting up all the way.
8) If you do have a kink, don't try to force it. If the catheter doesn't blow off, it will balloon until you can no longer hold the pressure and then you will end up with a urinary tract infection. Your wife/girlfriend can tell you how fun those can be.
9) If you have a balanced p-valve, make sure the bolt is open before ascending
(or don't dive with the bolt at all). Otherwise the air in the catheter won't have anywhere to go and it will blow up like a balloon.
10) If you're not sure you remembered to plug in, you probably didn't.
And finally, when you get a new suit first thing you need to do is take it out back, turn it inside out and piss all over it. It's going to happen some day, might as well get it over with.