How to clean Used Terrarium

[GarterPython]

Ok so as some of you probably know the tank that I use for y snakes actually is now empty since both of them died from a disease. Can't remember what it was. Anyway I'm going to house 1 or 2 leopard geckos in it and I want to make sure it is 100% cleaned down so that the leopard geckos don't get the stupid disease. So just put down any tricks you have for cleaning it down really good and making sure it is really clean. Also I have a couple hides and stuff I wanna use for the geckos too so tips to clean that stuff would help too. Plz help out and post stuff because I really need to make sure it is clean.