Contrary to what your rabbit might want you to believe, Wheat Thins do not a good rabbit diet make! (At least he didn't get into the squeezy cheese...)
A rabbit's diet should be made up of good quality pellets, fresh hay (preferably timothy, orchard, or other grass hays), water and fresh greens/vegetables. Anything beyond that is a "treat" and should be given in limited quantities.
Pellets should be fresh, and should be relatively high in fiber (18% minimum fiber). Do not purchase more than 6 weeks worth of feed at a time, as it will become spoiled. Pellets should make up less of a rabbit's diet as he or she grows older, and hay should be available 24 hours a day.
When shopping for vegetables , look for a selection of different veggies -- look for both dark leafy veggies and root vegetables, and try to get different colors. Stay away from beans and rhubarb, which are both toxic.
Hay is essential to a rabbit's good health, providing roughage which reduces the danger of hairballs and other blockages. When choosing a hay, look for a grass hay (timothy, orchard grass, etc.) instead of alfalfa. Alfalfa and other legume hays are higher in protein and calcium than grass hays and can cause kidney problems in some rabbits, especially seniors. Dried apple tree twigs also provide good roughage.
Note: When you feed a lower quantity of pellets, you must replace
the nutritional value without the calories, which is done by increasing
the vegetables. Also, a variety of hay and straw must be encouraged all
day long, we do this by offering fresh hay a couple of times a day.