This tip is geared more to those who are dating and getting to know each other. When out on a date, especially dining out at a restaurant, pay close attention at how your date treats the wait staff and/or servers. This serves as the perfect "litmus test" as to what to expect later down the road in the relationship.
Being raised in a French restaurateur family I have had the chance to observe all sorts of people...and over the years I have noticed that most people tend to fall into two main categories: those who treat servers with a friendly and kind attitude, and those who treat them with disrespect, disdain, and plain nastiness! The latter half are the ones that should automatically raise a red flag in your brain...no matter if it's a man or a woman!
If someone is overtly rude and capricious with a person they hardly know...how do you you think they will behave with someone that is familiar to them and hold no inhibitions toward several months or years down the line?
Bottom line: If you see any potential boy/girlfriend behaving like an asshole/bitch to anyone in the service industry, it usually means that in a relationship they will be looking for a slave (not the S&M kind)...so take heed and...GET THE FUCK AWAY WHILE THE GETTING'S GOOD!!!