Mac I’ve used a hammer and a tile snipper to break the tile where I want to.
Mac: Anger, a hammer, and a tile snipper! HAVE FUN!
A hammer and towel
Make a rock tumbler. Get a 5 gallon bucket with a snap on lid from Lowes or Home Depot. Use rocks to put in with the glass. You can shake it, roll it, rock it or whatever to get the glass to shatter inside the plastic bucket safely.
I have seen a few mosaics projects right here on Home Talk. They all put the glass pieces in a towel and break it with a hammer. After that, you will need adhesive, grout, and a large sponge. Have fun with it.