I use use a reptile under-tank heat pad. The heating pad is about 1/4 of the size of the tank. I chose this option over the heat lamps because of belly heat being more natural to them.
I have a 2 in 1 humidity percentage gauge and thermometer on the warm side (heating pad corner/section) that has a constant heat temperature of 83-86 degrees, and the other side of the tank is always 3-4 degrees cooler. The cooler side of the terrarium has a rock-bath that is big enough for her whole body to fit in if she gets hot.
She has eaten for me once, I've only had her for 2 weeks now.