Alliances and influance victory

You need good relations to get the option to form alliances, which means "Friendly" or "Close." This can be done by bribery, but high military strength does help. As for the Drengi: If it doesn't work to simply influence them, try a mass surprise attack on their colonies. It's often feasible to crush planetary garrisons & invade the worlds in the same turn, which prevents the AI from responding with its fleets. (I suggest maxing out your engine techs before you try a rush attack, though. The last three engines rock, no prepared fleet should go out without them.)

Yeah... Alliances.

I'm playing the campaign, first part (just got the game) and i have researched Alliances and would like to form an alliance with the Altarians (who are my teammates). We obviously have good relations already, but I don't know how to do it.

BTW, what bonuses do you get with an ally? Do you share techs? Anything?

I like how the game only considers tangible Military Might. By building one ship, my might jumped from 0 to 396. Then when I introduced the dregnins to a fleet of those ships, simply by placing them near one of their planets, they surrendered. I had expected more of a fight from them, and had allied with the other races in an attempt to use them to help me destroy them, after which I would kill them all. I guess that plan failed though, because when the drengins surrendered I won by a diplomatic victory... Kinda dissapointing, I saw a short clip of a planet and then instant victory as opposed to complete domination. O well.

Alliances and influence are broken... thank goodness.

You should go out to get your alliance FIRST then try to flip their worlds using influence. If you do it the other way around they will hate you for your "alarming influence" and are likely to declare war. If in an alliance however they will meekly sit there and let you flip world after world.

As evil on suicidal with no tech trading in 1.2 it is just about the only way to win. (Well the only way I can win).
Back a runaway dregnim or yor, make sure you snatch the influence resources and wonders, then when they've cleared the world of "goodness" start flipping all their worlds until you are strong enough to take them out.

To get that alliance in the first place, send your freighters to them, build spin control and make weapon heavy ships which stay in orbit. If they are friendly but not offering alliance then give them stuff.

So the only way to make an alliance is by them offering it?

"Alliance" appears in your trade screen when it's an option. It won't appear unless you're on good terms with the other race.