Do your work every day. Keeping up is easier than catching up. Talk over your problems with your professors. If you are having trouble with a subject, try reading up the subject matter of the following day's lecture. Start to work, real work, the first day, and keep it up regularly until the end of the term.
Every day learn the work given in lectures.
Keep your lecture notes tidy and up to date. College professors seldom set actual homework, but they expect you to know the information given in the lectures and to look up any points you do not understand. Keep a tidy, well-organized reference book, and learn your notes. College work is not exceptionally difficult, but there is a great deal of it. It is your own responsibility to see that you master that work.