There's a useful Apple-created tool built right into the OS:

1. Cmd-space for Spotlight

2. Type Storage Management

3. Hit Review Files

Now you can sort by largest files and quickly make an impact on space used.

The only problem I had with Apple's storage management utility is that it kept reporting a Steam game using 27G when that game was long deleted (and Steam itself was deleted). To resolve this, I had to go to the ~/Library/Application Support directory and completely remove the Steam folder (which didn't actually have that 27G game anywhere in it.)