Staples
Crickets,Woodies and Mealworms are the most commonly used staple foods for pet arachnids. While a tarantula may thrive on a diet of 100% crickets, it is always good to have a bit of variety. The size of your pet limits its range of foods.
A tarantula should be fed once or twice every one or two weeks. Dont worry too much about underfeeding your pet as tarantulas will go months without food in the wild.
Juveniles
60mm-100mm
At this size your pet can usually eat live crickets of all sizes and woodies if your tarantula is in the 70mm+ range. (Keep in mind that woodies are quite strong and can injure your tarantula if she is not large enough). Mealworms may also be used but its better to feed them pre-killed as they could burrow out of the reach of your spider.
Spiderlings
These are baby tarantulas, they range from 5mm to 50mm.
Spiderlings 5mm-30mm can eat live pin-head crickets (baby crickets), pre-killed small crickets or the back legs of meduim/large crickets. They can also be fed maggots at this size, but not as a staple. I personally dont use them, but they are a good source of protien. As your spiderling gets into the 40-50mm size range she can be fed live or pre-killed small crickets and pre-killed baby woodies. Mealworms can be cut in half and fed for some extra protien.
Adults
100mm+
These guys can be fed pretty much anything. Crickets of all sizes, grasshopers, mealworms, woodies and even the occasional pinky mouse.
I recomend you dont catch prey for your spiders as they could be carrying parasites or mites. Stick to store baught or breed your own.
Crickets woodies mealworms
http://www.thegreenscorpion.com.au/shopshow.toy?catnid=44070
