This is just stuff that i've personally found out from keeping my savannah. Other people are probably going to have different ideas of what you should do.
1. cage size for a hatchling, and adult.
My hatchling went from a 20 gallon aquariumto a 50 gallon to an 85 gallon in less than 6 months. Right now he's at 20 inches (not even halfway full grown, hopefully) and in another month or 2, he'll need something even bigger than the 85 gallon. They grow very fast, so its better to start out bigger. I'd recomend starting with a 50 gallon, it gives him room to grow, but its still small enough that he can catch crickets. I'm currently building a 6ft x 4ft x 4ft cage for him. Most people would say that's the bare minimum size of cage for an adult. You can't buy a cage that big, so keep in mind that you'll have to build it.
2. temps.
Most care sheets say 120-130 degrees is good for a basking spot. I find that if i keep mine up to 140-145, there's no problem and he seems to be more active. Some people even have basking spots close to 180 degrees, but it would probably be good to start around 135 and change it from there. You need to have a cool end of the cage that's about 85 degrees, so he can choose what temperature he wants to be. Make sure you have hiding spots in both the warm and cool end of the cage so he's not forced to hide where he's un comfortable.
3. feeding
Start with crickets then move on to pinky mice and then bigger mice and maybe eventually rats. You are going to spend A TON on food. The cheapest way to go is probably order a bunch of prekilled frozen mice. I've found that mine at 20 inches will eat about 3-4 frozen mice a week (dethawed of course). Its wierd, but he eats 5-6 live ones a week. I think the movement makes him more hungry. That's more expensive, but i figure its worth it so he reaches his full growth potential.
4. are they tame.
They are really skittish as babies, but most will warm up to with lots of handling. All of them are different, however, and you're not guarrenteed to have a tame one.
5. is a uvb light important.
No. There have been no studies to show that it is needed. Some people say it improves the colors of the monitor, but other than that, there are no visible benefits.
Good luck and check the archived forums. All the topics you asked about have been discussed dozens of times by many successful keepers and breeders
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Scott,
Proud owner of Porker the savannah monitor (currently 17 inches, 450 grams)