We did two types of cow-tipping in my day down in Valdosta. With the first type, you snuck up behind them in a field and hoped the farmer didn't catch you on his property. With the other, you snuck up on them in a bar after you'd had a few too many "kool aids" and hoped your buddies didn't see them leaving your apartment the next day.
Sorry if borderline inappropriate...just couldn't help myself!