Although you should not come across as bitter (as others have said), you should be prepared to give a short, non-emotional explanation of why you are looking for a new job.

The shorter the better, because what you want to emphasize is why you want the job you are looking for, and not come across like you are just looking to bail out of a bad situation.

Spend a good amount of time on your resume, and maybe ask other people to look it over. A good resume won’t get you an interview, but a bad one will make sure you don’t get one. Basics count: spelling, grammar, look, etc.

Maybe sure you have good references willing to give you glowing endorsements. Make sure you talk to them about it and have all the correct contact information. It is helpful if you explain to them the job you are interviewing for so they can be prepared to emphasize the relevant skills. If possible, get references from former managers and senior technical people. Don’t wait till after you send out a resume to try to get references together, things can happen fast, and you want to be prepared to take advantage.