I usually tip well in the 15%-25%range depending on service. The only time i don't tip well is when they bring my change and they decided to keep the loose coins and round up. They're lucky to a get a dollar after that. Imagine how much they steal a day by doing this.
I've found the newbies ive dealt with to be great people .i haven't had a bad deal with one yet so I will continue to treat them with respect just like i would anyone else .that is why we have a feedback section if they don't act right.