Depending on what the thoughts are, one possibility is to challenge them-are they really true? You have to work on it but it really does help.

Acknowledging them works. Then you can probe why you are having those thoughts and what you can do to change your focus or find a resolution.

How about accepting your thoughts as simply that--thoughts. They pop up, they move on, another one takes it's place, etc, etc. They are not truths written in stone, they are not forever, just a temporary annoyance. They can't hurt us if we deflate their power and importance. This doesn't include things like psychotic episodes, which are usually chemical in nature and need a chemical treatment.