A good tip that I've read on a lot of leopard gecko websites is to lay your hand flat on the substrate in the vivarium, and keep it still, as though it is an ornament. You have to be very patient but eventually, curiousity will take over and your leopard gecko may come to investigate by climbing on your hand and even licking you.
This is what we did with our leopard gecko that we acquired about a month and a half ago. He was very shy and skittish at first but after a while, he just got used to our hands and now he will let us pick him up whenever we want to. He's also grown very calm and cuddles up to whoever is wearing the warmest and darkest clothing

It's just a matter of time.