There is a visualisation I use. Starting with the root chakra, visualise it opening in to a beautiful red rose, see it shining a brilliant clean red. Then do the same with the rest of your chakras, working your way up to the crown chakra. Once they are all open and clean, start at your crown chakra and see the flower gently closing. Work your way down again to the root chakra :)

You can use the same flower for each chakra, as long as it is the same colour as that chakra, or you can use a different flower for each chakra. You don't even need to use flowers, you could just visualise the chakra itself. Whatever works for you