Influence

-Is your total influence = the influence of every planet added up, or are there some othet modifiers? (perhaps diplomatic relations?)

I believe your total influence is the cumulative influence of every planet. You can modify that, mainly by researching the influence branch on the tech tree, with structures, and by increasing your population. There is a tool-tip that shows you how a planet is generating influence. There are no other modifiers that I know of.

-Is it best to place influence starbases in range of as many as possible of your own high influence planets or is it better to place them on your borders to compensate for other races influence and try to swing their planets to you.

The proper way to use Influencer Starbases is to build them two or three squares away from a target planet, or in the middle of a system with several planets. And when I say proper, I speak as someone who has won most of his games with Cultural Conquest.

-How do you calculate every race's influence in a square

Don't know, don't really care to be honest. The Wikipedia site for this game probably has the specifics, if you really want to know.

I know of the tooltip in the planet window, but I never saw any difference after constructing an influence starbase (with modules)

I don't even see a difference after creating embassies and stuff, or could it be that this effect is so small compared too PQ and population?

Thanks for the answer so far.

I know of the tooltip in the planet window, but I never saw any difference after constructing an influence starbase (with modules)

Influence starbases don't modify the influence of your planets, but produce influence on their own, depending on the installed modules...

Okay, so say a starbase has modules to produce +20% influence, on what is that 20% calculated?

It isn't. The % sign is a misnomer, it actually adds 20 IP everywhere in its area of effect (plus whatever racial bonuses you have).

Also keep in mind that influence is cumulative. Influence Points (available for trade in your Foreign Relations tab) depend as much on your past influence as they do on your present influence.

Example: The Torians have 2/3 of the voting influence in the UP (happened pretty fast in my current game). If I take over all but six of their planets, they still have almost 2/3 of the voting influence a few turns later when we vote again, even though they're less than 5% of the galactic influence space.

Okay, I'm starting to see the light now, the % sign confused me quite a bit.
Thanks for all the input guys.