Below are some common behaviors dogs display when they believe they are above humans. Keep in mind that a dog does not have to display all of these behaviors to be in a dominant frame of mind. Sometimes an alpha dog will only display a few of the behaviors at random times, depending on what the dog decides it feels like doing at any given moment. Smarter dogs tend to challenge the pack order more than dogs of average or below-average intelligence.
Stubborn - OR, a dog that doesn't fully understand what's expected of them (has the command been fully generalized?)
Headstrong and willful - see above
Demanding - Could also be because such behavior has been inadvertently reinforced in the past
Pushy - see above
Begging - see above
Pushing a toy into you or pawing in order to get you to play with them - see above
Nudging you to be petted - see above
Sitting in high places, looking down on everything - OR, maybe the couch is more comfortable than the floor
Guarding a human from others approaching. People like to call it “protecting” but it's actually “claiming”—dog owns you. - Resource guarding can come from lack of confidence, it's not necessarily an "alpha" behavior
Barking or whining at humans which many owners consider "talking" (without a command to do so). - Again, could have been inadvertently reinforced in the past
High-pitched screams in protest of something dog does not wish to do. - OR it could be a leadership and/or training issue, lack of clear and consistent expectations of the dog, leading to frustration
Jumping or putting their paws on humans (without a command to do so). - OR it could be lack of training, and/or behavior being inadvertently reinforced in the past
Persistence about being on a particular piece of furniture when asked to stay off (dog owns it) - see above
Persistence about going in and out of doorways before humans - OR the dog has never been trained to wait at doorways
Persistence about walking in front of humans while on a lead - OR the dog may have not been trained to walk properly on leash
Persistence about getting through the doorway first - Already mentioned
Refusing to walk on a lead (excludes untrained puppies, dogs with injuries or illnesses) - Assumes that only puppies have been untrained to walk nicely on leash without pulling
Nipping at people's heels when they are leaving (dog did not give permission to leave) - Could be many reasons for nipping that have nothing to do with not giving permission to leave
Not listening to known commands - OR the commands have not been fully generalized and proofed to all situations, and as such are not quite as "known" as we may assume
Dislikes people touching their food - OR it could be a training issue, resource guarding either caused by the owner or not prevented with proactive training
Standing proud on a human lap - ??? If I sit on the floor my dogs will come over and either stand near/on me or sit near/on me because they know they're going to get some love!
Persistence about being on top, be it a lap or stepping on your foot - I think WAY too much is made of this
Persistence about where they sleep, i.e. on your pillow - It's soft and comfy and it smells like YOU!
Annoyance if disturbed while sleeping - There could be any number of reasons for this, none of which have anything to do with dominance
Likes to sleep on top of their humans - See above about dogs liking being close to their people
Licking (giving kisses) in a determined and focused manner - Both my dogs are huge lickers, and neither of them are particularly dominant. Assertive, bossy and determined, yes, but not dominant. (Halo!!!)
Carrying themselves with a proud gait, head held high - My dogs do that when they're happy and pleased with themselves, like when they've got a toy they especially like. You should see Halo prance around with her flyball tug!
Not liking to be left alone and getting overly excited upon the human’s return (see Separation Anxiety in Dogs) - This especially is not dominant behavior. Dominant dogs are confident, not anxious.