Summarize the following:
To make it easier to work with, find a flat surface big enough to accommodate your plastic sheet. However, you can't use the floor, as you need an edge to break the acrylic over later. Begin by deciding where you want to cut the acrylic. Measure it out, and use a ruler to make a straight line. You can mark the line with a permanent marker or grease pencil, or you can just use the ruler as a guide for your blade. Using your ruler as a guide, run a plastic scoring blade along the cutting line, trying to make one continuous line with gentle, even pressure. Pull the blade towards you along the line. It's especially important to get a straight line on the first go-round, as that line guides your subsequent lines. Run the blade over the line several times until you have a substantial groove. Once you do, flip it over, and make a line along the backside that follows the line on the other side. Score it several times as well. Place the line you've scored directly along the edge of the table. Using clamps to hold the sheet to the table makes the process easier. Break the sheet at the scored line by pressing down on the outer edge in a quick motion. You can wrap your hand around one edge and use your body weight to push down.

Summary:
Set the acrylic on a flat surface. Mark your line. Score the line in the acrylic with a plastic scoring blade. Deepen the cut using the scoring blade. Break the acrylic sheet.