I've done a few with friends but we always have the same rules:
1) always make 2 days out of it:
* day 1 is hell for the bachelor with a funny outfit going through town with different ridicoulous assignments, you know how it works.
* at the end of day 1: stay in a chalet or little house having "a few" drinks, playing cards, music etc (no drinking in daytime for safety reasons)
* day 2: some kind of activity (with hang-over) such as karting, paintball, airsoft, wavekarting etc...
2) ensure you have a theme that suits the bachelor: for example, I hate eating fish and anything that flies... so I had to wear a chicken suit and eat raw fish every time I refused an assignment etc
3) no girls whatsoever: no strip clubs, no strippers etc... It's just too dangereous.