I think of this question akin to what would I advise myself at 22 looking back now that I am 34. Here are some tips since time is an extremely precious resource and we all should utilize it as much as possible

-Take care of one's body through exercising, eating well, taking vitamins. This is huge since this pay off for extending one's life and minimizing health care costs for you down the road

-Learning both on the job and outside. The fact that you are on here seeking advice is a good sign you are doing this! Ask people questions especially those you respect and listen. Reading books/blogs/online articles are great exercises to learn about various topics. Joining organizations such as an alumni club, ToastMasters, professional organizations, volunteer groups, religious organizations are other ways to learn and meet new people. Plus it helps one network professionally and one can also serve good causes with volunteer or religious groups.

-Spend time with friends and family.You will never regret spending time with friends and family. I never heard of anyone at the end of their life wishing they spent less time with loved ones. I know after college one's social group often changes so joining organizations helps one expand their circle of friends. If you are in a romantic relationship, I would advise to spend time strengthening that relationship assuming it's a healthy one.