The shower's the best place, especially a shower stall. I really don't recommend two fully grown adults get too active standing up in a bathtub: it's rounded and slippery, and it's all fun and games til someone gets hurt :biggrin1:
I'm pretty strict about only playing sober, so I don't recommend that massive amounts of beer be consumed in anticipation of WS, but everyone learns at his/her own pace. Personally, I always go with my staple of lots and lots of black tea. You can drink it hot, tepid or iced as you like. Water, of course, is always good too.
I'd suggest a few urinations before the play actually begins. The actual urine should be as clear as possible and taste pretty neutral. If it's dark it's been sitting in the bladder a long time and is not especially appetizing. Also watch what you eat beforehand (up to 24 hours): asparagus makes pee smell really really awful, and I'm sure it effects the flavor as well.
Remember, urine is sterile: WS carries no risk for HIV infection at all, but some practices such as pissing up someone's ass/taking piss up your ass is high-risk and should be avoided with anyone with whom you are not in an anonymous relationship. And although I don't have any direct experience with this, I'd recommend that you not piss directly at or into a vagina at all, as the high PH in urine would undoubtedly cause some difficulties for the woman involved.
Have fun!