I've never written a manifesto before and when I looked up examples and advice it was really long and boring so I made up my own prototype and kept it nice and simple.
Hostile Take Over Group, Unlimited
Our Commitment: Take Over with Integrity
Our Goals: To annihilate Earth's population in order to utilize the natural resources and use the remaining ground as a garbage dump for our other planets.
How we will achieve this: Quick assimilation of the humans into our culture. There will be no rape, torture or suffering. We will be unbiased in choosing which candidates to retain. All humans who proclaim undying fealty to our ways and lifestyle will be kept as slaves without discrimination based on race, gender or sexual preference. All others will succumb to a smooth, painless death.
A little background: We have been studying the human civilization for some time now and have deemed it inferior. Please don't take this personally. It's just business. We have watched your moving picture shows that depict alien life forms as technologically advanced, but emotionally stinted creatures. This is not true. We are very caring beings, but practicality demands your extinction. We know that those humans who are lawyers and businessmen will understand.
One Last Warning: We have already disabled all your inferior physical weapons and will be using your strongest weapons, hope and love, against you by allowing you to volunteer for slave duty. All volunteers will be given first choice of their duty station and the chance to keep their puny lives.
Welcome to the Company!