Develop interest in the subject you are studying. Learning something that interests you is always easier to remember.
Connect the concept you want to remember to a visual picture. This approach makes it easier to recollect them later.
Understanding the meaning and procedure behind a certain formula or concept helps you to remember them easily.
Try solving and practising problems using the formula you want to learn. Repeated practise leads to memorization.
Writing down the tough formulas or concepts again and again, will help you remember them for longer.
When you have a lot of things to remember, the best thing is to write them on a sheet, stick them on the wall and read them regularly.