What's your plan in case of an alien invasion???
I would probably start by getting my family and friends safe in an underground base. Then start gathering supplies and weapons to start a rebellion. Then get people to fight against the aliens or die trying.
Probably not bother doing much, as many men smarter than me have stated - an alien race which has the technology to make it to our planet would be so astronomically powerful in our eyes that we would be no more to it than an ant is to us.
The only thing you could do is hope, and make yourself useful if they are looking for slaves.