Most rooms are not exactly square. Make sure you account for this when ordering. Measure and mark the floor so that there are no cut pieces smaller than six inches.
A straight wall can be a good starting point. If you do not have a straight wall, a straight chalk line should be used. When in doubt, lay out the critical tiles before cutting. Don't forget to account for doorways, hallways, fireplaces, etc. If you are doing borders or inlays, chalk line their exact location.
Prior to laying every tile, brush any yarn up that has fallen over the panel edge. Start by sweeping the concrete floor so the carpet squares will have no problem sticking.
Use a chalk line to make a registration mark where you will line up the edge of the carpet.
It is easiest to transfer measurements to the back of the tile and cut from the back. You can also scribe cut from the top using a 24" template.