In addition to what Federico mentioned, yes, you can use Google. In fact, at least from my experience, I'd say Google is generally better at searching SE than SE's search feature is. SE tends to rank pretty high in Google results, so just a normal Google search of what you're looking for is not unlikely to find it here. That said, you can also narrow your Google search to only look at our site.
For example, doing a Google search for:
site:aviation.stackexchange.com how can I search
will yield this question as the top result (or, at least it does right now.) :)
Also, to reiterate what other's have said, there's no inherent problem with duplicates. They will be closed as such, but, unlike other close reasons, that's not an indication that you've done anything wrong. If you search for the answer to your question and don't find the question here that already contains the answer, it's likely that someone else will eventually do the same thing. They will then find your closed duplicate question which will point them to the question that contains the answer. So, closed duplicate questions are still useful. We still want to close them, though, so that all of the answers to the question will be in one place, not scattered across several different questions. Also, it helps to prevent duplicate efforts to answer a question that has already been answered.