I have to agree with what others have said:

1) Understand the solution and why it works, if you can (google more if you can't!)

2) Try to find multiple solutions or confirmations for one of the solutions, especially if you can't fully grasp why the solution should work.

I should also say that as I've gotten better at SQL (or any programming system really) I find that the move from novice to advanced is not just about learning the solutions to common problems, but about finding tools that help trace new problems faster.