Things have changed so much from when I first owned a Leopard Gecko (LG) in the early 2000s. That gecko had colored sand, a heat rock, a heat lamp, and ate crickets or mealworms. I also didn't provide appropriate supplements...because I didn't know I needed to. Some 15+ years later, I know now better and I'm passing this knowledge onto my students.
Step 1: Gut Loading
Sunny eats Dubia roaches and Dubia only. When he first came home with us I had gotten mealworms because I was in no way prepared to deal with roaches and crickets are noisy, smelly, and can bite your lizard. Well, Sunny does not eat mealworms. So I had to track down a company with reasonable prices and shipping to get Dubias for Sunny. Sunny loves Dubias.
We gut load the Dubias with Flukers Cricket foods, this gives them all the nutrients they need and can pass onto Sunny. We tried raw vegetables, which the roaches do like, but we noticed the roaches were dying out way too fast (which means the money spent on them was being wasted). With the cricket feed, the roaches are lasting much longer and I'm not needing to buy them quite as often.
Another benefit of a Flukers type diet for your insects, you don't actually have to do anything special to gut load them before a feeding.
Step 2: Nutrients
Inside Sunny's tank is a little cap filled with Calcium that does not have D3. This supplement needs to be available to your gecko at all times. You might never see him lick it, but he will.
Calcium w/D3 should be provided to your gecko. Leopard geckos do not bask in sunlight and therefore need help getting the nutrients the sun would provide, this is where the D3 comes in. Lightly dust your gecko's live food with this supplement.
Herptivite is a multivitamin supplement that you also dust your geckos food with. Give this to your gecko at least once a week, but not at the same time you give the Calcium w/D3.
Do not dust with both D3 and Hertivite at the same time.
You cannot skip vitamins and supplements if you're going to own a Leopard Gecko. These nutrients are they only way to prevent against Metabolic Bone Disease. Google Leopard Geckos and MBD and you'll see what I mean. It's really sad and really painful.
Step 3: Feeding
Sunny is old and was a former stud, so I like to think that he was used to a certain kind of lifestyle and is too lazy to chase after his food. He's also pushing 8 years old. We hand feed Sunny using either blunted forceps or small tweezers.
First we (the students, myself, or my husband) pull out a couple of unlucky Dubias and dust them. In the first photo you see heavy dusting--this is probably way too much, so Sunny's next feeding we will skip the dusting. Once the bugs are dusted, we start 1-by-1 grabbing them, generally by the leg so that they dangle and Sunny sees them move. He prefers his food still kicking.
If your gecko bites onto the feeding tool, do not pull it away. They will let go. If you pull or jump, they could injure their mouths.
Step 4: Feeding Continued
Depending on the size of the roach, Sunny can eat anywhere from 3-6 in one shot. He's generally fed every second or third day. We weigh him frequently to make sure he's not getting overweight and if it seems like he's gaining, we might skip a few more days---this is okay! As long as his tail is still nice a plump, he can go a good bit of time without eating. Geckos store fat in their tails. When the tail starts to look too plump/swollen OR super thin, then you have problems.
Step 5: Water
A dish of fresh water should always be provided. Occasionally we will spray the inside of the tank or wet the paper towel around Sunny's water dish to increase humidity (to help him with shedding). You will see your leopard gecko drink, it's super cute.