Brad, lots of this depends on the environment that you are keeping your animals in. Say, for example, you are keeping them in a garage in western Sydney where your winter temps get below zero then you will need to provide 24 hour heat (at least over winter). If, however, you ahve them in a herp room with other enclosures (like where I keep my hatchies) then you will require a lot less heating.
so, what you are trying to achieve is a hot spot where they can bask to warm themselves up. This spot can be quite hot. I have some that get up to 70 degrees. But then you also need the rest of the enclosure to be cooler so that they can regulate their body temperature. As they are a cold weather animal the rest of the enclosure need not be above 30 degrees but the cold spot certainly shouldn't drop below 20 degrees. I do however regularly notice my animals out basking on days that only get to 18 degrees.
The other thing to remember is that you need to provide UV. I understand that the halogen lights Cris is talking about above do give off UV so that is a good idea. You need to confirm hwoever, if that UV is filtered out when you ahve a glass cover over the bulb. Alternatively, you can use mercury vapour globes as they put out heat and UV or you could use one of those screw in fluros but remember that the maximum wattage for those is about 26 so they won't provide a great deal of heat. Of course, that is not a problem if you live in Bundaberg but it would be in Sydney. Of course, you ccould spuulement a UV fluro with a heat mat or similar to provide that little bit more.
Also with UV lights remember that the UV only works for about 6 inches. The reason I use the 26 watt fluros is that the lizards get really close to them to bask and this means they are also receiving good UV. If you were to use, say a 160 watt mercury vapour you migh find that yoru animals dont need to bask too often so they wont get their UV requirement.
Another way to provide UV is to allow your animals to get unfiltered sunlight for at least half an hour per week. If doing this you will need an escape proof and predator proof outdoor enclosre that also allows them to get out of the sun.
And when yo do set up your tank make sure that you have a few thermometers set up so that you can read the temps in the enclosure.
And just a couple of questions that will help us: Where are you? What size enclosure are you keeping the animals in? What materials is the enclosreu made out of? What have you done for ventilation? What type of room (i.e. bedroom, shed, back verandah etc) is the animal being kept in? All these things will hcange the type of heating we would recommend.