If you can get your hands on them, find some major study guides, preferrably print ones, as I find I can't study for long periods of time in front of the computer - failing that, I always resort to a number of superb sites online for my study and review. For Chemistry, I would advise http://www.chemguide.co.uk - the individual that wrote the pages has broken down the concepts to a level at which one could self-learn Senior Chemistry.
As far as forgetting the material that you study, try and make links between the material - don't try and rote learn it - it's not all about facts and figures. Chemistry is meant to make sense, and is meant to describe the world around you.
When you're studying start with a basic concept, or a broad, overarching topic and create a mind map from there, linking all the points that relate. Not only does it help to link concepts, but images are often easier to take in than words.
If you need more help, or want some advice, feel free to PM me, I'll see what I can do.