First thing is to pull out all the seats and the console if it has one. Remove the kick panels, seat belts, and the sill plates. You might also need to loosen up the lower rear quarter panel covers.
I always install the rear section first as the front section overlaps it.
As ODZKing wrote, do not cut off anything!
When you start to do the front, make sure it is centered, which you can tell by looking at the sill plate areas. Also slide the carpet as far forwards as you can. It won't go all the way up the firewall, just partway. Make sure there is some overlap over the rear carpet.
If you have a floor shifter, cut slits over the down rod, linkage, and shifter, and start working the carpet over them and then under them. Do not cut away any sections of carpet unless you have to. Nothing worse than putting the console back on and seeing too big a hole under it.
Put your rear seats and console back in. Now is usually a good time to locate the holes for the seat belts, cut a 1/2" hole over each, and reinstall the belts. Then put the kick panels and sill plates back on. You also need to locate the dimmer switch, cut a hole for it, put the rubber grommet on, and slide the carpet over the switch.
Once all the is in place, and the carpet is pretty much in position, get a screwdriver or icepick and slide it up from below the car using the holes for the seat studs. Look for where the carpet pushes up, or the pick comes through, and cut about a 1/2" hole there. Once you have the four holes for a side made, reinstall your front seat(s).
