Its best to score it repeatedly and then break it over the edge of a table top leaving a clean break. Using a rotary tool like a dremel or a saw is just going to melt it. Most lowes and homedepots will cut glass and plex for free to your specifications.
If using a saw you need to cut deep so only the front and back of the saw blade touches.
So on a table saw jack the blade up really high.
Also pick a wood blade with a fine edge, more teeth the better.
Score and snap is always a great option if you are doing a complete run across a piece.
I use a table saw. 60t blade and works great. slow feed rate.
I don't like to snap too long of a piece (over 6" long) as it does not always snap like glass. hard to get even pressure on the piece while snapping.
table saw works great.