Based on a few experiences, here are some guidelines for tipping servers:
Don’t taint others opinions based on your separate experience. Just because you don’t like the server based on your interactions does not mean everyone needs to not like them. Let them be their own judge. For example, this girl had a bad interaction with the server and then the other guest came to the table and was telling them how horrible the server was. Now they got an attitude like the server did something to them and now they don’t want to tip the server. That aint right!
Read more here at Restaurant Etiquette: Guidelines for Tipping the Server.