Diet is the cornerstone of preventative health care for all pets, but exotic pets in particular. Most exotic pets have fairly strict dietary needs, so find out what your particular pets need, whether it is the right balance to prevent metabolic bone disease in reptiles or enough roughage for your rabbit. Our understanding of dietary requirements is in really in its infancy for many exotic pets, so you may need to change feeding habits as new information becomes available. Check current care sheets for your pet to see if there is room for improvement in your pets' diet.
Also keep in mind that obesity is a major problem for many kinds of pets, including exotic pets, and this can cause many health problems. Stick to healthy food choices, avoid overfeeding, and increase exercise opportunities if possible.
Exercise will help combat obesity as well as boredom. For some exotics this resolution will not apply (it's hard to get a sedentary frog to work out). However, for many pets, you may want to look at increasing time out the cage for socialization and play, or increasing cage size to give them more room to move, or perhaps adding safe accessories such as solid surface wheels for running or wood for climbing. Again, look at current care sheets for your species to see if there are ways to improve your pets' activity levels.