Capital ships are dangerous for their abilities, not their damage output. Unless the enemy capital ship(s) are leveled up and have extremely dangerous abilities (like a L6 Marza or something), if you want to hurt the enemy's ability to deal damage, target their frigates instead. Generally, don't focus fire on their cap.

 Also, if you have heavy cruisers, they're strongest against enemy LRF, but often will not move in to engage because they're too far away: often, you should manually order your heavy cruisers to attack enemy LRF.

Also, depending on how large fleets are, it's a good idea to have your carriers either kite or sit right on the edge of the gravity well so individual ones can warp out when you can tell they're taking significant damage.

Ships are generally good at targeting what they're most effective against.

What I like to do with my siege fleet is to keep them positioned on the edge of my gravity well. When the enemy starts warping in, I tell all my siege frigates to warp out to attack the enemy's planet while he's attacking your gravity well. Unless the enemy is prepared with a scout mob, he might have to retreat some of his ships if he doesn't want to lose the planet.

You probably don't want your siege fleet with your main battle fleet, especially if you're on the defensive: they die very easily, have next to no damage output, and have a high replacement cost. Same for your antistructure ships.

Your carrier ships should almost certainly be with your main battle fleet.

How do i make a ai player ally with me if they keep attacking my fleet/planets  ?

On a 1human  vs 1ai player game is it possible to make the ai player ally with you ?

Sorry for the endless question but am confused about the following aspect of the game.

Can ai player give credits,metal,crystal to you to aid in relations ?

I can improve what any ai player thinks of me simple enough but how do i improve what i think of them enough to go past the 3.50 relations rating so i can get a ceasefire with that ai player? 

Are missions worth completing even if it means opening up a hole in my defenses at the start of the game ?

It really depends on what difficulty you're playing against. If you're playing against anything other than Cruel or Vicious, it's very simple to set up a starbase or two at choke points and watch your other enemies suicide their entire fleet on it (if they attack you) - this allows your own fleet to go and try to complete a mission the AI you're interested in asked you to do.

It also depends on whether you'll have enough resources to get a cease-fire with the AI - it might be easier to complete a mission than to get the relationship bonus from some other source (like expensive research, or expensive donations to the AI). For some missions, it's relatively easy, even without doing anything: sometimes the mission will just be "Kill Ships: 5" and if the target enemy sends a few ships to attack your starbase, you can just sit back and watch and the mission will be successfully completed.

This is just a thought, but it might be possible to boost your relationship to reach that key point of a cease-fire by sending envoys to one of that AI's gravity wells - one with very few ships, or the envoy'll be shot down immediately. If you can, use the envoy's abilities to increase your relationship with the AI.

However, if the AI's main battle fleet arrives, the envoy will be in serious trouble: if this happens, you should have a couple envoys in reserve, ready to warp in to the AI's gravity well at a moment's notice. When the first envoy starts taking serious damage, activate the ability to make it invulnerable, and then order it to warp out a few seconds later while telling one of your other envoys to warp in. Kite around, repeat. If you have 4 or so envoys, you'll be able to keep this going almost indefinitely. (You always need to have an envoy at the gravity well or in route ASAP so that you don't lose the relationship bonus from the gravity well)

That's only an idea though, and requires a lot of attention - it would only be worthwhile if it's too difficult to get the AI to like you any other way.

These numbers are useful to know:

https://www.sinsofasolarempire.wikia.com/wiki/Simple_Diplomacy_Modification

especially the

"offerOrAcceptTreatyHappinessThreshold:CeaseFire" value of 0.5 - that's the magic number you need to get to to get a cease fire going so you can start sending envoys.

I remember once I was trying my best to get an AI to like me but wasn't able to quite reach that 0.5. In the end I had to scuttle one of my fully upgraded planets to remove the "Adjacent Territory" penalty, and I was finally able to get a cease fire, envoys, and then recolonized.

I'd already done that and had reached the limit of relationship increase due to credit donations and couldn't go across the whole galaxy to attack some other AI's civilian structures (the mission I got). This was the only thing I could think of doing. This was before I'd thought of the kiting-envoy trick I just mentioned above.

It didn't help that I accidentally wiped out that AI's whole early-game fleet on one of my starbases. He absolutely hated me (but everyone else hated me even more).

I looked at my up-to-date gameplay.constants file, and it says 0.5 as well... given that that file specifies the diplomacy constants, I find it quite unlikely to be wrong, but maybe it is. I'm currently testing it out... I could be wrong, I haven't played against the AI in ages.

Yes I played an AI game today and I'm pretty certain that it said 3.50, and that I really could get a cease fire at 3.50.

        breakRelationshipThreshold:CeaseFire 2.0

        relationshipRequirement:CeaseFire 3.5

You're looking at either the Original Sins or Entrenchment files, not Diplomacy.

Is there anything ive missed ? what do you do in order when you try a get a ai player to be allied?

To improve what  faction a  thinks of you:

send credits,metal,crystal

complete mission 

send envoy

To improve what you think of faction a:

offer a mission to faction a to send a envoy to your homeworld 

Be Advent. Upgrade max allegiance via research.

Or relocate your HW.

Those are the only ways.

Basically, a mobile phase jump inhibitor? The only things which come close are the capital ship abilities that can slow, stop, or disable an enemy's phase jump or engines, such as Ion Bolt and Gravity Warhead.

Scale, complexity, and pacing are all much closer to that of 4X than most real-time strategy games.

LF are good against carriers, support cruisers, and flak frigates, iirc. However, they're countered hard by the LRF and not nearly as good for killing capitals.

When you start a game is it always best to fast track to two miltary labs to get the LRF ?

Is the light frigate any use in mid-late game or are they just suicide vessels ?