How can you tell if someone is doing coke?

How can you tell if someone is doing coke?

OK, theres a lot of ways, trust me, my husband and I are both ex-addicts.
For one, there will be an increase in energy.A grinding of the jaw, grinding or continuously moving it. Their pupils will change,they will get edgy.
If their doing it I.V, you'll know right away, everything will change,Look for track marks, not just in the crooks of their elbows like you see on t.v, you can do it anywhere there is a vein. The backs of your arms, neck,back of your hands and top of your feet! Stomach and breasts.