Congratulations on the lucid, even if it was a short one.

There are actually a lot of different ways you can prolong a lucid. Some of the most common are looking at your hands or rubbing your hand together. It would help if you didn't get too excited at becoming lucid; that definately makes it end faster. Of course, a lot of times that's easier said than done.

But like anything, it takes practice. I have confidence that you'll get better at it soon.