Always depends. Sometimes I will have already tried it and forgotten to mention it in the original post. Sometimes advice given could be impractical or impossible to try, sometimes advice may need clarification/explanation, sometimes advice given is derived from a misunderstanding of the question.
When the advice isn't on troubleshooting, it often isn't appropriate to just try it out. If I asked what product to buy for a given purpose, and someone suggests x product, I wouldn't simply go out and buy that product before perhaps asking some more specific questions, or asking how it compares to y product suggested by another user.
(this applies to any forum I go to)