There are some very basic things you can do to stay in a dream. One (and my favorite one) is to rub your hands together. Even if it feels like the dream is completely gone and your rubbing your RL hands, keep rubbing. Another great one is to start spinning around (coupled with rubbing its very effective). Finally, the moment you become lucid, take off yoru clothes. I know it sounds weird, but it helps you become more aware of your dream body, and that’s the key to longer dreams.
Here’s a great article from the knowledge base: Prolonging Lucid Dreams