This is from my "Jackson Chameleon Cage Build" album, but the principle will work with any species.
If one places the heat lamp in a corner, on the top of the cage, and then runs a branch from that corner, to the dead center of the cage.
The bulb used should provide the highest temperature desirable for the animal, immediately under the lamp, where the basking branch lies.
This way the animal can bask comfortably on the branch without "screen climbing".
To adjust its temperature, the animal merely has to move up or down the branch.
I find this setup to be a good place to start when working with a new animal/species/enclosure/equipment, as it is fool-proof after its setup.
Just make sure to check temps often, to make sure the animal is not exposed to temperatures too extreme for it to handle, or too low for it to function properly.
I recommend trying different wattages of bulbs before raising or lowering a basking-bulb fixture.
The drift-wood I myself am familiar with is not ideal for chameleon enclosures. Some nice fresh-cut branches from a suitable tree should work out better for the animal.