To make your Lucid experiences last longer try frequently reminding yourself that you are dreaming, actually say out loud things like - "This is a dream!" This should help you stay aware and in control for longer.
In terms of increasing the vividness of your dreams; you can also try vocal commands, but you have to believe they will work (just as everything in lucid dreams, you are in control.) Have a go at shouting - "Increase dream quality!" or "Make dream clearer!"
Also a couple of simple techniques to help towards both problems.. Take your time to look around at your surroundings in your dream landscape, and move around using your sense of touch on nearby objects, the floor, the air, smells - i know how tempting it is just to take off and fly around, but practice the basics first as it helps.
Alongside the spinning around technique you can try rubbing your hands together as well which will keep you focused.
I hope this helps you out and best of luck for your future lucid dreams