OmniDiskSweeper is really great at what it does: showing you the files on your drive, in descending order by size, and letting you decide what to do with them. Delete away, but exercise caution.
I was helping a friend find where the space on her MacBook Air had gone, and realized I hadn’t recommended OmniDiskSweeper yet.
A previously paid App by The Omni Group now free. Still works perfectly, and is the best way to find what’s eating up your space. Can’t recommend it enough.