"1. To attack enemy ships in space with multiple friendly ships at the same time, do the friendlies have to be organized into a single fleet? The other day I noticed that when I shift-click individual ships and give them an attack order, they arrive one at a time and are of course picked off."
Yes, they need to be in a fleet, otherwise you get the trickle-of-death syndrome.
"1(a). If I select two friendly fleets and give them an attack order will only one fleet attack at one time? (I seem to recall this is what happened to me a couple of days ago.) Thus, is the only way to attack with all my ships at one time is to put them all in a single fleet?"
Sometimes you'll get lucky and they will, most of the time it needs to be a single fleet. HOWEVER, if the first fleet fights to a draw, the second fleet will renforce the first and they'll both fight in the second combat.
"2. If I colonize a tiny planet and it allows only one facility, will I still reap the benefits of a research center if I put one there without a space port?"
No. You need to have one space port per system before you'll get *any* points from any facilities in that system.
"2(a). Is the same true if I put a system computer, etc., on a one-facility planet?"
If you put a SYSTEM computer on, you'll get the benifits.. on all the other planets. If you put a regular computer on, you'll gain exactly nil.
"3. What exactly is the relationship between size of planetary population and other things such as production? In MOO2 I could easily see the relationship but here it's unclear. Does getting it up to a particular level vastly decrease production time of new units, etc.?"
More poplulation = more production. There are several plateu levels that I don't remember offhand. Happyness does the same thing, only it's easier to measure- a jublient pop produces more than a happy one, which produces more than indifferent, etc.
"4. Do mines I lay in space affect my own ships (haven't had a chance to test this yet but I'm curious)?"
No.
"5. Why does the AI attack me so early in the game? I'm playing with medium settings and I've noticed in the few games I've played that even if I've given another empire a gift when I first meet them, they haul off and declare war a few turns later, no matter what. Often they claim I've been doing this and that, even though I've been having no contact with them and haven't even researched any kind of intelligence apparatus, much less built anything. What gives?"
Some of them are just xenophobic.
Phoenix-D