One of the most effective exercises you can do in your job-search preparation is to go through everything you write and everything you may say in an interview and ask "why is that important?" Scrutinize every word you may write and ask yourself why it is important to the hiring manager? That's the important part. Why is it important to the hiring manager? It doesn't matter if it's important to you, just to the hiring manager.
For instance, you may have included on your resume a training program that you completed at a job 10 years ago, on a program used only in that company. Why would that be important to the hiring manager? Ok, I'll give you the answer to this one: it probably isn't.
If you can re-word it to put the focus of the importance on what the employer wants than it should stay, otherwise, toss it out.