1. Set up three bases: One in the US, just like Visser One did. Anything that mirrors her ideas is going to be a good idea. The second is in Japan, which seems to be replacing the US as the center of technological advancement. The third is in the United Kingdom, which is on good terms with just about every other country on the planet.
2. Make the humans think we're here for a good reason by fixing their biggest issue, apparently called "Global Warming", also known as "Climate Change". As good as sea-level rise is for us, it's equally bad for humans.
3. Stealthily establish a fourth base somewhere in Africa. AIDS will be a good cover for us.
4. Take advantage of the humans' fears, especially those revolving around December 21, 2012. The more they worry about "the end of the world", the less likely they will be to notice what we're doing.
5. Adjust the laws, rules and regulations in a matter that gives us more power, as long as the humans don't notice.
6. Exploit human diseases when possible. First matter of order on this: Autism, followed by diabetes and the various cancers.