It depends a bit on what type of knowledge I'm looking for. A Google search can often get me really far for both personal opinions, as well as general knowledge. Most questions have already been asked and answered many times before on various websites, so you can often find the answer without asking yourself.
If your question is not something that has been asked, discussed, or explained on a website already, then I would head to a Musing type of website, such as Quora, StackExchange, or Yahoo Answers. These works a lot like Musing, but you don't earn Steem for using them of course. So go there and ask your question just like you would here on Musing.
Another great alternative is to ask someone in a asking style Reddit subreddit such as /r/explainlikeimfive. This subreddit allows people to ask question, then other users will try to explain it in a very simple way, like a five year old would understand it. This is a great resource for asking questions about science or something like that, since the users will always try to explain it as easy as possible.