First of all, know your dog and what type of toys he does best with. If he is a heavy chewer, he will need very durable strong toys. Small dogs will want small toys.
Some dogs like squeaky toys or plush toys. Some like bone-shaped toys while others like balls or other toys that roll around.
Make sure the toy looks safe and that it will not fall apart quickly. Kong is a good brand and there are other good brands of strong tough toys.