Pets are an integral part of the Realm of the Mad God experience. They aid you in battle and bring your character to its maximum potential. The most important abilities in a pet are Heal and Magic Heal, at max level they are equivalent to having hundreds of Vitality and Wisdom. For a third ability, Electric is highly recommended as it will paralyze enemies in place that are close to you. You max pet abilities through feeding your pet, and when maxed you can fuse two pets of the same family and tier to upgrade your pet to the next tier.
Pet ability hatching
Different Pet Families have different chances of their first ability, and the last two abilities are evenly weighted. Humanoid family is one of the best for hatching Heal and Magic Heal. Every Family can have Heal first at least. Here you can buy eggs ready for hatching. You can hatch higher tiers like rare here to skip the common and uncommon tiers of hatching.
Hatch until you have perfect abilities
If you do not have a pet that is Heal and Magic Heal as their first two abilities (any order is fine but if you have to choose go for Heal first), and Electric as its third, you should keep hatching eggs until you get one. If you have just Heal and Magic Heal, you can keep it temporarily as the last abilities aren't unlocked immediately. The third ability is only unlocked when your pet reaches higher tiers.
Feed your pet using high feed power items
To be efficient with your fame/gold usage when feeding your pet, you should try to feed your pets with the highest feed power items you have available to you, as the cost to feed a pet is based solely on the tier of your pet. Here we have the highest tradable feed power items readily available for feeding. Book of Gebs are recommend as they have 800 feed power.
Only fuse your pet when at least the first ability is maxed
When you feed your pet enough, its abilities will reach a max level based on the tier of the pet. When you fuse two pets, the pet on the left in the fusing window will keep its abilities. The maximum level the abilities can reach is based on whether or not both first abilities were maxed on the previous pets. Always make sure they are maxed first before you fuse, otherwise your pet will permanently have a lower than maximum cap and the pet will be ruined. You can max the second ability as well to have a bit of cheaper pet feeding.