The main thing would be to keep them free of dust, dirt, and any sticky substances (eg oils). The dust and other particles (eg metal shavings) are one major cause of these threads sticking, and the oils and stuff will contribute to these particles becoming stuck there.

You'll need to do this both for the lens and any filter you're going to screw onto it (or the camera body and lens back).

• Use a cap over any lens back thread while it's not screwed onto a body.

• Use body caps on bodies stored without lenses.

• Keep any screw-in filters in a case while not screwed onto a lens.

• Keep a lens cap over the lens when not in use. However, this still exposes the front thread while you are shooting. If you were paranoid, you could use a clear (UV) filter or a filter ring with no glass on the front and remove it when you want to attach a filter ... or just try to wipe any dust or grit with a soft dry cloth before attaching anything.

Another major cause of sticking is deformation of the thread, such as from dropping the lens. If you have dropped your lens and slightly bent any of the thread, it may stick and that may be hard/impossible to fix.

You also need to be careful about what you screw into the filters - say you buy an old lens or filter from ebay, and the thread on that is damaged, that thread may then also damage the thread on the lens or body you're screwing it into.

Cheap accessories may also have deformities in the threads or be slightly misshapen from spec even when new. This could be a problem.