I think my strategy for the colony rush is different that most people's from what I've read in these forums. Many people have fine tuned it, I haven't, so they may have a better way of doing it. But I'll let those people post themselves.
What I do, and its worked for me upto suicidal so it can't be that bad, is:
research planetary improvements pretty early to get the +10 in research and production; also space militarization I think has the +10 for military production. Other techs I get early don't really have much of a bearing on the colony rush. I find the speed techs take to long to get another +1 movement (2 techs you'll have to get). I think the first sensor tech gives a + so I'd get that. Basically i look for techs that will take only like 3-4 weeks. However, fertility acceleratioon, or what ever one comes first there, is nice at the beginiing. The AI gets this early.
I set spending to 100%, and the sliders to 33% each, with maybe some adjustment to get a tech on an exact week. Taxes to keep 100% approval for a while until I'm about to go broke.
I land my initial colony ship first to relaunch with a full load. I rush buy my second colony ship on the spot. Rush build a factory and queue up a second the alternate between markets and factories, with a lab thrown in. Then I'll buy my colony ships after they are partially built, depending on my cash situation. My home planet tends to be my only colony ship maker. When the launch I send them blindly to a cluster and hope for something nice. I choose a direction towards my oppents first to help keep the border away from my home planet. It will depend a lot on what the galaxy looks like and where I am in it.