Simple question, simple answer:
Believe me, it will make a difference!
Stackoverflow can be a life-saver when a complex problem pops up. However, starting to share your answers yourself or ask good quality questions can be a bit intimidating at first.
Once you have an account, there are various ways to help others even if you're not sure about writing answers yet.
Vote on questions & answers (or star them). This helps finding them again later and motivates others spending time to help.
Edit outdated answers, and update them with new information.
Comment (min 10 reputation, quite frustrating if this is blocked for your) to engage in answers/questions. Will really help you if want to dig deeper is someone else's question.
Finally: start asking your own well documented questions and answers. By voting up or down, you'll have learned what makes a question easy to answer or rather hard to understand.
Stackoverflow is one of my favourite ways to find answers and give back to the community by posting some answers myself.
What are your experiences with it? Interested to hear the story!