Pets need stimulation as much as we do. Playing with them is a great bonding experience and they know they are loved.
Easy Toys: of all the toys our dogs have, their favorites are made from ropes and socks. Tug of war play with the ropes plus chewing on them (acts like our flossing) keeps them happy.
Teach Them to Play Catch.To easily teach your dog to catch things from the air, or to want to catch a ball or frisbee in flight, start with having him try to catch popped popcorn (perhaps flavor it if he's not a popcorn fan) - it floats slower and gives him time to figure out how to catch it. Do not feed him much, though, so he will still eat his main food - it's still a treat.
Keep your dog active. Unless you really try to get your dog to be active, he will usually spend all day just walking around, lying down and getting very little quality exercise. Even in a big yard, unless he is provoked into running (maybe by a squirrel), he'll just spend the day napping and walking, and running maybe just a little. Most dogs will be so happy to just see the leash - to see something different and to spend time with you!
Make a habit of walking your dog daily, or at least playing catch and frisbee with him to get him moving. For overly hyper dogs - get him to be physically active for 2-3 hours a day in order to keep him calm - he has too much energy to run off inside a house or fenced yard. Other dogs do well with an hour or two - but make it an active time - chasing, running, walking, hiking - get him moving.
Cheap Toys... Your pets need playthings and toys to keep them occupied. You need not get the most expensive - pets respond well to cheap toys as well. However, don't buy toys made in China - many of those are known to be made with potentially toxic ingredients. For example, birds like beads hanging on string - you can make your own versions with thick string and large solid beads (not fragile ones). Dogs can have a blast with a 2 or 3 liter soda bottle, with the labels taken off and tightly capped to make sure it's quite full of air, not limp. Or try a plastic milk bottle that they can push it around and try to lock their jaws around the slippery round body of the bottle. Make sure to remove a toy once it's destroyed or while you can't watch the dog - in case a piece breaks off and he tries to swallow it. Toys only last so long but are a great source of fun. Old tennis balls are great - once they lose the bounce and are no longer useful to you, let the dog have it. Take old towels, tie a knot in them and toss them around for the dog or cat. Bones are not good, as they can harm teeth, splinter, or break off pieces that can choke or be barfed up later. Look around and see what is safe, and you'll soon have a great choice of toys for your pet.
For a great toy that has lots of lives - take an old sock and a tennis type ball - put it in the sock and tie the sock. Your dog can entertain himself gnawing on the knot and the bounciness of the ball. If the ball squeaks that may be a bonus. If a hole is chewed into the sock, just get another sock and do the same with that ball. The dogs love this and eventually chew the ball out of it, but even just a sock with a knot in it - seems to occupy them by playing with it.
Have a puppy? They love to be wild, play hard, chew and all. Get appropriate toys for the age and size. Make sure a puppy gets a lot of exercise!
Used Tennis Balls- make sure the tennis balls you give your dog to play with are used and beaten up already. New balls have a dye on them that can be picked up from the dog's saliva, and it's not good for them. Just give them what they enjoy best anyway - a good, used tennis ball. You should probably wash it first.
Exercise Your Pets. Your pets need to exercise just like people need exercise. Birds should be allowed to fly or walk around to get their exercise, in an enclosed area so they don't escape. Dogs need to run or walk daily - if there is no yard, make sure to walk him and take a ball or saucer he can chase. Cats usually can get around on their own, as well as fish - but make sure there is ample room for them to swim or wander. Pets need to metabolize their food, so they don't get obese. They need to work their heart rate with activity. Movement will help them poop, else they may get constipated.
I once had a lazy dog (he had shorter front legs than long legs and tripped up easily), and one day, with no warning, he went to sleep and didn't wake up. He didn't get enough activity (his choice - I tried) and his heart just gave up on him. If you have a pet that doesn't like to be active, check with the vet - he might require less vigorous activity, or he might need to get more activity - figure out what is fun for your pet - following you? Fetching for you? Being chased? Make it fun for both of you and see how healthy you both can be. It will make your pup so happy that you engage with her.
Spend Time With Your Pet. Your pet loves, trusts, and depends on you. You need to spend time caring for and communicating with your pet (maybe fish aren't so dependent on your company). Clean up after them, feed and water them daily, and play with them. Dogs and cats will just rest with you, hang out with you, and be with you. Pet them, play a game with them, exercise with them, and show them you care. Let your birds fly and walk around your desk area or sit on your shoulder. If you make a routine of exercising with your pets - it will help both of you. Walk your dog, play frisbee, jog, bike, hike - dogs enjoy doing all of that with and alongside of you. And chances are you will enjoy the activity by having a partner in doing it with you. That means better health for you both! Both physically and mentally.