1 - Cell phone usage
Taking selfies, browsing, texting and making non-emergency calls when you are with someone is disrespectful even when they aren't buying you dinner.
2 - Talking about exes
You're there to be with that person, not obsess over someone else. Also, running an ex down makes guys wonder what you'll be saying about us, and waxing poetic over him shows you really are ready to move on.
3 - Talking over the other person, changing the subject, not listening or being dismissive
You're there to get to know each other, and communication should be going both ways without derailing. Having someone interrupt, change subjects, not know what you were saying or just wave you off means they not only weren't interested in what you had to say, they weren't interested in you enough to show you the most basic courtesy.
4 - Bad manners
Being polite and respectful not only to your date, but to those around your date, is a must as we are known by the company we keep and therefore we reflect upon our date. Using cell phones or electronics in movies, cussing, or otherwise being a disturbance to others is just embarrassing. Your date should not have to apologize for you.
5 - Being rude
People who treat others poorly to impress someone or because they feel it is acceptable not only reflect poorly on their company, they also tend to inevitably unleash their behaviors on their company once they are no longer trying to impress.
6 - Entitlement
Expecting everything without having earned anything is disrespectful of the other person. If someone takes the time to do something for you without strings attached, either take it gratefully or don't take it at all.
7 - Flirting with other people
If you are with someone, be with them. I actually knew a girl who went to sit with another man she didn't know to share drinks with him while she was on a date, and then chase her date down to ask her why he left her there.
8 - Expecting a ride home on the first three dates
Until you get to know someone, you are looking for reasons to weed them out. Nothing is more awkward than sharing an after goodbye forever ride home in the same car.