Folding the stroller yourself is not about being nice; it is about preventing damage to it. Different models of strollers fold up in different ways, and the ramp personnel do not have time to futz around trying to figure out how it works. They will just cram it down if it isn't obvious, and if it breaks in the process, well, it breaks. (Read the fine print on that gate-check ticket, and you will note that there is a statement that says that the airline is not responsible for damages.)
To minimize the chances of anything getting damaged, remove all toys, etc., anything in the basket, and the hood. If you don't need the item on the flight (such as the hood) put it in your checked baggage before you leave for the airport. If possible, I recommend folding the stroller before you head onto the jetway; carry it down or drag it on two wheels. It is best to secure it shut with a bungy or luggage strap, or as I do, wrap something around it to protect the upholstery from grease. (I made a cover, a piece of ripstop nylon with velcro on it that wraps around the stroller; it doesn't cover the handles or the wheels.)
PS: Different airlines have different rules about whether or not a gate-checked stroller counts against your baggage allowance, and whether it counts as a checked bag or a carryon. Go to the website and check.