My dogs Abby and Bailey have slept in our bed since they were babies. They are small Bichon Frises and luckily, don't take up too much room.
As most normal dogs who are allowed in bed do, Abby usually curls up at the foot of the bed and goes right to sleep.
During the winter, she will cry until you lift the covers so she can scoot down to the bottom of the bed and sleep in the same spot, but under the covers!
Bailey is a different story. He enjoys sleeping under the covers at all times with his head on the pillow. If, during the night, you roll too close to him and he feels he doesn't have enough room, he will stretch all four paws out and try to push you back to your side.
There are many mornings when we wake up and he has drooled on the pillow!