College is a lot of unstructured time. That makes it easy to fall into a trap of laziness and unproductiveness. I try and avoid that and purposely structure my time. Here's what I found that works best for me to do everything I want to do socially but still maintain good grades.  
       
        

1. Find the involvement level that works best for you 
       Some people prefer to be in just a few activities that require high commitment levels. Others prefer to join many activities that allow participants to to miss a few (or many) meetings.
    That being said, don't over commit yourself but also don't under commit yourself. When you have too many meetings and activities to attend, you won't have any time for homework or studying or even relaxing! But if you have too little activities and too much free time, it becomes SO hard to actually get stuff done!
Keep in mind the level of involvement on campus that you're looking for stuff to do outside of the classroom.
         I am in a sorority and on a club sports team. These are both incredibly time consuming and so, to my mother's disappointment, I haven't joined any clubs yet. However, I have a position in my sorority and so it's been a great opportunity for me to get leadership experience.

2. Prioritize 
        Write a literal list of stuff you need to get done. And then order them by whats due tomorrow, later this week, next week, etc. Start at the top and work your way down. Once you get done all the stuff that's of immediate priority, it's ok to take a break and do something fun :)
        Or this is my less enthusiastic approach to it:
      In between class and activities, get everything due tomorrow done. After activities, I do everything that isn't as urgent because I have a few days to do it. And if I decide I'm too tired to keep getting stuff done then, it's ok because everything important is already done and so I just go to bed "early."

3. Plan social activities around things that have to get done
         Meet friends for study sessions if you're both taking the same course.
         Or better yet, I plan most of my social things and catch ups with friends around meal times. We both have to eat so we might as well do it together and kill 2 birds with 1 stone :)

4. Find how you study best 
Some people study better alone in a completely quiet environment. Other people like to study with a group of people. I've learned that I do NOT study well with my best friends! If you like to study in groups, find a group that you study best with! I hate studying in my bedroom but my roommate loves it.

5. If you have to get a job, let it be one that you get to do your homework at
I'm currently an office assistant and I get to do my homework in between checking in clients and scheduling appointments. Most on campus jobs pay around the same amount so I enjoy being able to have a job that doesn't completely tire me out!

6. Schedule your down time/free time/fun time
I find it so much easier to get work done when I have something to look forward to. I like to make time to go to my club team practice during the week and to go out and hang with friends on weekends. I look at these events as "deadlines" for me to get my homework done by. That way, while I'm at practice or out with my friends, my mind is on what I'm doing and not what I have to do later.

7. Be productive during the day and then just relax at night/go to bed early
Nothing against night owls here... but my friends (and myself included) who are productive during the day instead of fooling around and doing who knows what, tend to be able to go home and just relax at night. I'd rather get all my work done during the day instead of having to stay up super late at night because I know that I'll do crappy work/won't absorb what I'm studying/give up and go to bed early anyways. And plus going to bed early makes getting up the next day so much easier ;)

8. Use all your time efficiently 
If I get to class a few minutes early, I'll check my emails then. That prevents me from feeling the urge to check my email mid-lecture and stop paying attention. If I have a few minutes before I need to head to class in the morning, I'll wash out my mugs from my morning coffee right then instead of saving them until I get home that night or I'll write my to-do list for the day then so I can collect my thoughts.

9. Keep your room clean/ organized
I save SO much time by knowing exactly where each object in my room is. It makes being in a rush so much less stressful. I never have to worry about misplaced homework/calculator/phone charger/etc. My trick: PUT EVERYTHING AWAY AFTER YOU USE IT.

10. PLAN
I'm a huge planner but even my friends who aren't tell me they benefit from having some sort of a calendar/ planner. I personally have a planner I use for class work, a calendar on my wall for meetings/ larger events, and a phone calendar for every event in my day. I have a print out of my class schedule above my desk. I write sticky notes for each class that are mini to-do lists for that class. It can never hurt to write it all down!

Bonus tip:
Coffee.