Please don't take-up a slot on a new Horde match only to quit after a few rounds--please play deathmatch instead. It's disrespectful to the others who are looking for a longer Horde game challenge with others who are also interested in ringing the bell at round 50. When you leave, the matches become slower and more difficult for the rest.
Also, if someone in a Horde match builds and upgrades a turret, unless explicit consent is given, it's rude for you to jump on it unless the builder is dead. If you want a turret, save your money and buy one.
That is all. :)