Heres how I take care of my leos :-]
First off, you can keep a baby leo in a 10 gallon but I highly recomend getting a bigger tank for him as an adult, such as a 20long. The reason being they will not be so cramped, has room to roam and exercise and also more room for you to put cage stuff in :-]. As for heating a UTH (Under Tank Heater) works well, and you should use a termostat with it (this is so the UTH doesnt overheat)and the temps should be 88 on the warm side and 78 or room temp on the cool side. Since Leos are nocturnal you will not need any lighting.
For substrate I recomend paper towels or slate/tiles, this is so they cant get impacted on the loose substrates. He will also need two hides (one on the cool and one on the hot side)and he will also need a humid hide (which is one of the hide boxes filled with peat moss, bed a beast, ect) and keep moist, this helps them shed quite a bit and they can also get more humidity if they want. you should also two bowls, one for water and one for calcium powder, I highly recomend Minerall, or Reptocal. He will also need vitamins, herptivite is a good choice. These are too be dusted on his prey idems, say, the calcium every other feeding and the herptivite once a week.
For feeding, I use crickets, mealworms and superworms (only give the supers to adult leos) you can also use silkworms, and waxies/pinkies (these are treats, use very rarely) I ussually rotate between these food idems to give my guys some variety. Leos will do well on a stable of mealworms or crickets. Your feeders should also be feed well, I put my mealworms in a mix of oatmels, bran, grain cereal, wheat germ and sometimes powered milk. I also use a gutload formula found at www.gexfiles.com, this forumla is more optinal and many different people use different things. Also I feed my adults every other day and babies every day.
As for getting a leo, I strongly recomend going with a knowledgable breeder, there are many who post on this forum. This way you can get a healty leo, unfortunently many leos/reptile sold in pet store tend to be very unhealthy and sickly.
Also read as many caresheets as you can, the webpages at the top of the forum are good places to go and also pick up the Leopard Gecko Manual :-], and good luck!