Don't bother with prom/semi formal type things unless you already have a girlfriend beforehand. Your friends will most likely be off doing something else with other friends, and the entire experience is mediocre if you have no one to enjoy it with.
Get a job as soon as you're able. You'll meet new people, which is always a plus. Don't worry about not being able to hang out with friends (they'll be too busy to hang out anyways), or not having time to finish homework (grades aren't that important, as long as you don't fail anything). Also, down-time during jobs (like if you're a cashier and no one's in line to buy anything) is a good time for conversation with co-workers/friends.
Take a co-op class if/once you can. Makes your resume look good.
Get a job as soon as you're able. You'll meet new people, which is always a plus. Don't worry about not being able to hang out with friends (they'll be too busy to hang out anyways), or not having time to finish homework (grades aren't that important, as long as you don't fail anything). Also, down-time during jobs (like if you're a cashier and no one's in line to buy anything) is a good time for conversation with co-workers/friends.
Take a co-op class if/once you can. Makes your resume look good.