In no particular order, these are most of the tactics that some might consider gamey or cheap:
http://www.spaceempires.net/home/content-36.html
And some min-maxing info:
http://www.spaceempires.net/home/content-1.html
Note that some people consider lowering happiness down to 80 or 50 for some more points, but I do not personally care for that...