It starts with an innocent gesture or a good faith gift and ends with you being a slave or killed. Aliens are deceptive, evil creatures that hate you and will do whatever it takes to get you out of the way. For all you know, the aliens use people as fuel to power their flying death squads. Or maybe they need some guinea pigs to test a new drug the want to put on the market. Either way, you need to know how to kill them and keep them from coming back.
Guns kill aliens very well. Especially big guns found on tanks. Throwing water on an alien will only piss it off, making your death all the more likely. Acid that can kill you can probably kill an alien just the same. Be careful not to spill any on yourself.
Chances are you are going to have to kill the aliens yourself because you can’t trust most politicians and they’ll screw us all over. Don’t let your congressman vote to sell you out to the aliens. Worlds have been destroyed due to some Ass Clown in the government making deals with the aliens. Write your congressman on the dangers today.
Steal the alien’s technology. It’s not enough that you blew it’s head off, steal that hyper death ray that vaporized the idiot next to you and kill some more aliens. Take that cool hover bike and pick up a friend for some good old alien killing. One person can drive while the other shoots.
Find other alien haters to get your world back. Ten guns are better than one. You don’t have to like your Alien Death Squad, you just have to shoot aliens with them. Remember, joy riding in an alien ship will piss them off, but shooting an alien with an alien ship kills it.
Does it piss you off to find out some jackass wrote a virus that has wiped out your computer? Use those people against the aliens. Any advanced race worth a damn has some sort of Internet type thing. Find some lonely teenage nerd to make a series of viruses to make those alien bastards cry. Get an army of angry teens to take over their flying ships and crash them into each other.
Taking it to the next level
Find out where the aliens live and mess up their home world with their own technology. Don’t send everyone, someone needs to stay behind and make sure none of those alien bastards don’t invade again.
Learn their language. Not all of it, just the swear words and some cool insults is enough. Sharing a quick quip in alieneese right before you incinerate one is much more satisfying since your insult is the last thing they hear before dying.