Congratulations! Lucid dreaming is great fun, and I've had some sporadic success with it myself. One of the things I've leant is that having a strategy is important. In the beginning (and I am also a novice at this, but have gotten good advice from various good sources) the most important thing is to 'stabilize' the dream, and your own mental and emotional state. Going lucid in a dream can be very exciting, and this excitement (or fear, or whatever) itself can often knock you out of the dream. So if you don't already, I suggest picking up a daily routine of meditation, to get some control of your thoughts and emotions, which should solve this first issue fairly quickly.
Secondly, you need to stabilize the dream environment, by 'anchoring' yourself into it. The best way to do this is to engage your senses - touch things and really feel them, listen intently, look at things up close in detail. If you can find a mirror in the dream (if you are in a house that is familiar to you for example, or have a sense of where a mirror might be), then looking at yourself in a mirror is also a good way to anchor. Only once you can stabilize yourself and the environment properly does it make sense to move on to object manipulation (just like having consistent dream recall before you move on to attempting to become lucid makes sense, since otherwise you wouldn't remember it even if it worked). Once you then get good at manipulating the dream environment, you can move on to messing with physics, jumping in a superhuman way and so on, and eventually flying. When you have mastered flying, you can start experimenting with some more advanced things, like teleportation, going straight up as far as you can, opening and closing your eyes in the dream, or meditating and doing magic and the likes.
Finally, if you find that you often 'slip back into' the dream after having gone lucid, you need to learn to ignore the dream narrative. Strategy is, again, important here. Things will try to distract you in the dream. A giant flaming fish will pass by and you will want to follow it. Don't. Have a clear plan in mind of what you want to do (stabilize, manipulate objects, physics, whatever the case may be) and stick to it. Rehearse your plan whenever you intend to attempt lucid dreaming, and you should be able to stay focused and not get sucked back into the dream narrative.
Good luck, and happy dreaming!