Well the old way, I was taught to check was to put the E-brake on and hold the brake. Have the engine running and in gear. Then let the clutch out and the engine should die.
The other way is to actually look at the clutch. There is an inspection slot at the bottom of the bellhousing. You should see a sheet metal plate on the bottom covering a gap between the engine and the bellhousing. Laying down, and look up and you shoud be able to see through a 1/8" gap.
