Taking care of yourself mentally and physically is a good way to have a good memory. This means a healthy lifestyle - the right diet and exercise and all that. If you go to Metapsychology, you can read a psychologist's review of Dr Steve Ilardi's book ("a splendid book"). He's one of the top experts on lifestyle - headed the U of Kansas lifestyle-depression project.
Memory for muscle skills - just plain practice.
Memory for things around the house - To Do list, writing things down. When you don't have time to write something down, improvise. If there's a bill that you forgot to pay, put it in front of the front door.
Memory for things you learn in school -
For remembering course content, the first thing is to take good notes. This is not a skill we're born with. It takes a lot of time to learn doing it right. A source I like very much for how to do things - WikiHow. Read their article on how to take notes. It's great.
From my experience as a uni student, the two most important principles are organization of information and practice.
Write detailed outlines, with phrases, short sentences, and short paragraphs. Keep your lecture and reading notes separate but if you have a really hard test, you can take all your notes and combine them into one big outline. You can even - if it's REALLY hard - make your outline into a set of flash cards and memorize it.
Don't have papers all over the place. Have a filing cabinet or file box. When you don't have time to file things, keep them together with paper clips or folders, stacked neatly.
Don't cram at the last minute. Periodic review during the semester is smart. Another practice method is to occasionally rewrite your notes after class, which makes them better, with more details. Flash cards are useful in a number of ways. I found that I could make the cards work better by adding some mnemonic devices to them - a word or drawing that triggers a memory. The key to mnemonics is having things so weird you can't forget them.
Always study for an essay test and a very good way to do this is to write your own questions and answer them. This gives you a set of phrases and sentences you can use while you're taking the test and you have to hurry.