The best thing would be if your lights sat on screens instead
of being free on clamps. If you can't do this right now, then
use some backup twisties (garbage bag twist ties or whatever
you call those things), and secure the cord in a few places
extra to whatever you've got the lamp clamped onto. It'd be
best if this was done at a higher level then the lamp is
attatched at, that way if the clamp gives, the lamp will not
fall into a lower position, possible too close, burning your
animals. I've seen pics. of snakes that have gotten onto lamps
and suffered horrific burns, these are "wild" animals that can
not understand the concept of something being so much hotter than
would be natural and will not avoid an open bulb inside a cage,
but will get burned horribly if they have access to it. It's
crazy I know, but you gotta look at it like a reptile, they just
don't "get it", that there's a danger.
Better than twisties would be those plastic zip-ties. You can get
these at like a Home Depot or Lowes, even Wal-Mart's gotta have
them.
As long as your domes are rated for the wattage you use or less
you should be OK, I don't like the plastic socket domes, but
rather use the ceramic heater domes, the ceramic socket can
take more heat. Don't touch bulbs with your bare hands, as
the oil on your hands can cause it to blow when heated. Handle
new/cold bulbs with a dishtowel to keep it oil-free. Er, I
wouldn't really handle hot bulbs at all. lol! 
niki,
NC State Certified Fire Fighter II