Race doesn't matter when it comes to scores.
Difficulty level doesn't seem to matter much either.
Victory type does make a difference. Military Conquest definitely scores the most. The other victory types seem to score about the same although perhaps a Tech Victory scores the least.
I remember people posting something a little more quantitative about this but I couldn't find it nor do I remember very much, but if I recall correctly there was something about a military victory being worth 2.5 times the base score. What a base score is and what the other victory conditions are worth I don't know, perhaps someone else will know this.
Size matters. More specifically the number of planets matters. The more planets, the higher the score pretty much end of story. Picking abundant everything as well as scattered systems or perhaps loose clusters is the best way to go, for some reason dense clusters seems to result in far fewer planets. Also the number of resources in the galaxy to mine can make a huge difference. I think it's far more important to get the lion's share of the galaxies resources early and hold onto them than it is to colonize the most planets.
As far as strategy to get higher scores there are a number of things. There are four components of score; Social, Tech, Economy and Military. These are reflected by the graphs that are shown in the timeline section of the civilization manager. Getting a high value in any or all of these components of score won't necessarily add much to your score, you need to have high values in these components that are held for a noticeable length of time before they have significant impact to your score.
Concerning your Social score it's definite that your population is a prime part of this component. I also strongly suspect that the overall level of your influence contributes to this. There is also some possibility that your approval is part of this as well although I tend to doubt it. Clearly maximizing your population over long periods of time tends to increase this component. Also I would recommend that you grab every influence resource you can get. I know some folks that are uncertain whether or not influence matters but it seems that games where I've ignored influence resources have a lower Social score than games where I haven't.
Your research score seems to be dependent on only your research spending. The tech rate you select doesn't seem to matter. Also whether or not you have any techs to research doesn't seem to matter. Money spent on research even after the tech tree is complete counts as much as anything else. The number of techs you have or whether or not you researched them yourself doesn't seem to matter. This component is one that you can spend a lot of time and effort on for very little return. I've had games with significant amounts of research that I doubt have ever been equaled and the Research score was extremely disappointing. To put this in context I had 5 separate PQ32 research planets all of which were surrounded by 16 economic SB's giving me total research bonus of 384%. My top research planet was giving me over 16,000 RP's per week and the least of my five main research planets was giving me over 10,000 RP's per week. Besides the 5 PQ32's I had close to 50 other planets that shared in at least some of the bonus from the economic starbase arrays that were optimized for research. My total research exceeded 200,000 RP's per week. It's a little tough to correlate but I suspect that research perhaps added about 30K to the score of that game. Very disappointing.
Economy is a component that you can get a lot of benefit from but it does take *very* high levels to get something noticeable. I've gotten reasonable results from having income in the 1.3M bc to 1.6M bc per week range held for on the order of two to three years. This obviously requires a good amount of economic resources (usually 6) to mine. This is also where alignment can help. If you're evil you can build the Mind Control Center which gives a 100% global economic bonus. Finally, there's the luck of getting (and keeping) the Economic Prosperity event that doubles your economic output.
Military ranking is another area that can be maximized. This is simply the sum of all your attack points plus defense points plus one tenth of your hit points. The bonuses supplied by military starbases as well as the Spin Control Center count in this calculation. So of course do the bonuses supplied by military resource mining and racial ability as well as the bonus you get when ships are in orbit (not quite sure the value of this bonus).
As I mentioned earlier you need to do these things for long periods of time to show any noticeable benefit. To be used to the best effect, doing things that increase your score should be an integral part of your strategy that you employ from the beginning throughout the entire game. Thus building a military SB array early to pump up your military ranking helps you to avoid wars that you don't want, helps you to end wars that you don't avoid on more favorable terms (such as being able to demand a number of your opponents planets as part of a peace treaty) as well as increases your military score over time.
Finally, with all other things equal, ending the game earlier versus later scores higher. The all other things equal part is what's usually in question.
I have my own personal theory about how length of game works. It seems to have applied to every game that I've ever played although I've seen the breakdowns of scores from other folks, some of which fit the following data and some of which don't. In any case as I said this is my own personal opinion so take it for what it's worth.
If you look at the four individual components of your score and sum them they usually don't add up to the total score that's reported. In general the longer the game, the bigger the discrepancy between the sum of the component scores and the total reported score. This seems to correlate well, although as I mentioned there are some games that seem to violate this. In any case based on my games I've come up with the following percentages. The following lists the reported length of game in years. In each case these games were all ended Dec 22. Since ending a game anywhere between Jan 1st and Dec 22nd all count as the same number of years, it's probably always advantageous to end the game Dec 22nd. In any case the following lists the game length in years and the ratio of the total score to the sum of the four components of score.
5 years = 87%
6 years = 78%
7 years = 66%
8 years = 58%
That's the only data I have. I'd be interested if folks were willing to post data from their games to see if we can extend and/or validate this theory.
In any case it's clear that the longer a game goes on the more points you'll accumulate but on the other hand the less credit you get for them. There is a balance with length of game and potential point increases. It doesn't seem that you ever really get to the point where score starts to go down but there's no doubt you get to the point where it's not worth the effort to continue the game. Where exactly this point is depends a lot on what's going on in the game. If your pop is still growing fast, or if your income is growing fast or military rank is growing fast then it's probably worthwhile to continue the game. If nothing much is growing (and growing fast) there's really not much point in continuing.
In any case some people seem to think that you can take any game and arbitrarily extend it and get pretty much any score you want. Please feel free to try it and let me know how that works out for you.
