One way is to get a fresh notebook and make notes from a detailed textbook/revision guide. It's good to use colour, graphs and pictures/drawings where possible as using visual guides helps a lot.
Some people I know have a notepad, the size of their phone, where they wrote all the info from on Unit. They use a different notepad for the different units and every morning on their way to school on the bus they just read them.
I also like to revise by making a really long presentation on the Units of the subject i'm studying. Just by making it and checking over it helps you revise a lot as you are practically revising for a long period of time. When i finished the presentation i simply left it playing on my pc in a loop and kept checking it troughout the day for over a week... This takes up a lot of your time so it's not the best
If you have a close friend who is also revising for chemistry you can both get a text book and ask eachother questions from the different topics or present the units to each other as studying from others is easier than from a textbook...
Hope this helps ^.^