I read that population is the key variable.  All the research, manufacturing, etc is based on population.  So with that in mind I focus on population growth, expansion, and research.  I only have to build a few ships to make my military rating just high enough to discourage the AI from attacking me long enough for me to get medium/large ships that move 10+ per turn and then I easily take over all the races.  This method has made it easy to win on normal and the next diffucult level.  But at tough/genius level, the AI outproduces me too much and I get overwhelmed by their ships before I can build my big/fast ships.  For my next games I will look into increasing my production/manufacturing to counter the AI bonuses.

To enable discussion, here is how I implement the population and research strategy.

I use a custome race with plus to speed, research, population growth, free first building on new colonies, and double population on new colonies.  But this also works pretty well with stock Terran.  I usually play on large/huge galaxies with 6 AI opponents.

First, create a new colony ship design that is the cheapest possible.  It will have low sensor range, low life support range, but will not cost much to rush buy or will also be quicker to build.  This ship is used when you already know about a planet and it is close to your existing planets.

Next, create a new colony ship design that has 4 sensor range, moves 3 or 4 per turn, and has a decent life support range.  This ship will be used to explore and colonize.

First turn:

- rush build the colony ship with 4 sensor range

- rush build a research building

- click govern your homeworld and put all resources into technology (0 wealth and 0 manufacturing/production)

- choose the green colonization technology that gives +10% growth

- explore with all the ships, even the survey ship. it can be switched to survey after you find your first planet

You should get this technology in 2 or 3 turns, depending on the bonuses to your starting planet.

Second turn:

- load 1B people onto the colony. it will become 2B people when it colonizes due to the racial ability

- rush build another high sensor colony ship

- explore

At this point you will have spent about $3k of the starting $5k

I keep my home planet on 100% research until I get the first two technologies for growth and sometimes a bit longer.  So Around turn 10 I switch to mostly 50/50 production/research on my homeworld.  Only a bit later do I move the govern slider to include wealth.  I do not bother to micromanage any of the govern sliders on my colony planets though.

When I get my first planet I take Pragmatic and take the three free constructors.  I then upgrade them to the colony ship with 4 sensor range.  This usually costs about 100 each.  From then on I take Benevolent to get the free colony ship and the extra planet near my home.  I usually play on huge galaxies so I normally get at least that far down the Ideology tree.  But once the colonization phase ends, I sometimes do not have enough Ideology points to get any of the buildings that produce Ideology.  So I think I need to reprioritize selection here.

I do not understand the technology trees well enough to know what is even close to optimal so I tend to get a mix of techs reactivly.  When the AIs start threatening I increase my diplomacy.  When my populations are unhappy I get moral increases, when my populations seemed to be maxed out I increase the farming.  And so on.  It seems to be a balancing act to grow my population and military research as fast as I can while holding off the AI opponents until I get big and fast ships.

At normal difficulty level, I usually have the most planets and then as a result  am first in population, economy, and a few other areas.  The down side to this strategy is that I never seem to have many ships and my military rating is always low until I build the big ships.  But then I usually have a tech advantage and my big ships can take over the AI players, often without losing any ships myself.

But again, this strategy seems to fall apart at the higher difficulty levels due to the AI bonuses.  I would like to hear some other strategies though.

jsmartel i have some suggestions about improving your early game strategy. 

I too first research the growth tech but not at the expense of building colony ships and factories ? I do not think that you benefit much by gaining that tech 3 turns earlier, and consequently be behind on a factory and 30% of a colony ship.

Second, since your pop doubles on landing, does it not make more sense to load it chock-full, because you will gain more pop which means more prod ? If the planet can sponsor the shipyard of course. 

Nice tactic with constructors

Thanks for the reply annihilator.  About the colony ship population, my thinking is that I do not want to reduce my home planet population much, because it is the source of my production.  Also, with the constructor trick (not my idea, by the way, someone else mentioned it on the forum) you will be sending out three colony ships on the same turn.  There just is not enough population on the home planet to max out all the colony ships.

If you are doing custom race I have found the cheese combo of Ancient and Patriotic is over the top. Combine that with Clever +2, and Production +1. I mega cheesed my game by setting Habitable to Uncommon Planets, Uncommon Habitability and Rare on Extreme, (Insane, loose clusters). I went over the top further by seasoning the galaxy with 'common' precoursor relics since I get a game breaking (10%) cumulative bonus to research for each relic mined. 

I tend to use Earth and Mars. 

One of the i races starts with two planets if the iconians start with 1 planet it must be the iridium 

anyway once you get the last level of terraforming that planet is pretty much a solid blob of adjacency bonus's