If you use the round plastic or mercury strip thermometers you probably wont get a correct temp. If you still decide to use them you need 2, one of the cool side and one near the basking area.
The best to use are digital thermometers, they are expensive but they are acurate. The best one is a temp. gun. They arn't very expensive, they are small and tell you exactly what the temp. is. It can go up to any temp. unlike other kinds that only go up to about 100 degrees.
Heat mat-not the best either. Most of them give off a certain heat that is simply too hot and also burn animals. It is much easier for them to get burnd if a loose substrate is put on top and the animal can dig down to it.
Bulbs-many bulbs are safe and if placed correctly are fine. But if placed directly on a screen top, an animal, especialy a snake may be able to get to it and easily get burnd.
Heat tape-probably the best to use. It can be controld so the animal gets the perfect temperature it needs for basking and no burns. It is cheap, can be cut, and is very safe.
Low humidity (0-30%) -stay clear of live plants (except cacti), not alot of water, dont use subsrates that hold moisture.
Moderate humidity (35-60%) -live plants, more water
High humidity (65-100%) -lots of live plants, large amount of water, frequent misting/spraying of the cage, subsrate that holds moisture.
Another thing that helps raise humidity well is by playing the water bowl on the warm side of the cage.
Misters and Foggers are also wonders for raising humidity.