In addition to all the correct answers, I have to agree that the search features of StackExchange are not exactly inspiring. I myself often think "I think we have seen this question before", but when I go and look for it, I can't find any duplicate. It always seems to me that I am only able to find a duplicate if I remember at least some words of the question title.
As such, for a new user, I would propose to do a quick search, and if you can't find a clear answer, just go ahead and ask your question. If it is closed as a duplicate, you at least know where to look. Always remember that a question being closed is not an insult, and does not cost you reputation on the site.