What is the correct way to mount a lens

[verncoc]

Some time ago I cracked a lens by screwing the lens holder to tight. This was one of Light Objects cheapest lens mount. I have read that some people use O rings, silicon and other things to mount the lens in the holder. I find it difficult to keep the lens centered. If nothing is used. I'd like to hear how others do it.
Vern C

[TLHarrell]

If the lens is very loose in the holder, cut a strip of tape and roll it around the perimeter of the lens. Build up enough layers that it fits snugly. If it gets too tight, rip off a half inch of tape.