Determine your priorities and goals. If you need to maintain an A average because of a scholarship, the amount of time you spend studying will be different than someone who is happy with C's.
Make a schedule. A planner or program that helps you schedule your time is a necessity. Write in all of your classes, then allot at least two to three hours of study time for every hour of class time. In subjects that are more challenging for you, expect to spend even more time studying.
Plan time for friends and things you enjoy doing. Try to schedule this time so you are not tempted to cut into your study time. Having fun and hanging out with friends are important parts of the college experience -- as long as you maintain your study time as well.
Keep up healthy habits. Make time for the gym and for eating three healthy meals. Most campuses have a fitness center students can use for free and cafeterias in or near dorms. Neglecting your health is a sure-fire way to throw a hitch in your other plans.