Getting a raise is an excellent move because it doesn’t require you to trade more time for more money. You are putting in the same amount of time, but pulling a bigger paycheck. 
Freelancing is the next best thing to being paid more for your full-time work, because professional work always pays more than unskilled.
If you have enough experience in your field to coach others with their careers, then create a website — or, if you have one, add a section describing what you’d offer as a coach. 
Whether for high school students or adults, you can monetize your expertise by teaching people with less experience or knowledge than you in that subject area. 
Many offices need temporary workers, so old-school companies like Kelly Services do still exist and list such opportunities.
If you’re handy and generally available to run errands, sign up with TaskRabbit or Zaarly, or just put a notice up on Craigslist to get groceries for time-crunched people or do general handy person tasks.
If you’ve got wheels, you can earn extra money shuttling around those without through Uber and Lyft.