Myth: Dogs like to be scratched on the top of their head. Many dogs will back away if you reach over the top of their head to give them a pat, Since their field of vision does not include the area above them reaching over their head makes many dogs nervous and may cause them to react.
Myth: A cat laying on his back wants a belly rub. In reality, few cats enjoy to have their bellies rubbed. When a cat feels vulnerable or in danger, laying on their back allows them all four legs (and four feet of claws) to defend themselves. Reach for them when they are in this position and you may be mistaken for the enemy.
What do dogs like best? Many of my furry canine friends love rubs under their ears - preferably both sides at the same time. Scratches on the lower back is another favorite as well as long soothing rubs down their sides.
My kitty friends always enjoy rubs on the sides of their neck and they respond happily with purrs. My cat Tiger loves to have his face rubbed between his eyes down his nose, this really seems to calm and comfort him, but he is the only one I know who enjoys that. Many prefer to come to me, rub around my legs, and then walk away with out wanting me to reach out to touch them.
The number one rule: Never reach out to touch a a dog or cat you don't know. Bad experiences from their past could cause them to act out due to fear or pain. Everyone has their preferences but their purrs and wagging tails always communicate their happiness.