I'm often presented with a list of answers where one just barely is the best answer, so I give it a checkmark. Is there anything to do with the two other good and useful answers besides voting them up to make clear to readers that they should check those out, too?
The Canonical* Answer
So you've got a solution to your query but it took a combination of the answers provided to reach a solution. Start off by detailing what you did, provide credit (with links) and block quotes to the other "solutions" provided. From there continue going in to details and whatever else it took to get to your solution.
As an alternative you can select the best answer already there and edit it to make it the best answer to your question. Which route you choose is really up to you and how much work is involved but the result is the same, you now have a super high quality answer to your question.
But why stop there? You may have had a very specific question with regards to a particular feature, function, or problem. Sometimes the solution isn't even related to that feature, function, software, or problem but a larger problem instead. For instance, this question about "Pencil" based on the answer for that question you can see it has nothing to do with Pencil at all but rather just installing XULRunner on Ubuntu. Based on that information you can broaden the scope of the question to make a fantastic canonical question which later users can find and be linked to.
* Not Canonical the company, the adjective of canon