A newbie writes:

[DirectorTsaarx]

Jon:

You're close: it's condition improvers, then resource improvers, then atmosphere converters.

As for happiness: it depends on your "happiness type". Oddly, for "neutral" races, just colonizing a new planet decreases happiness. They also don't like treaties, unusual events, building warships (I think), enemy colonies in "your" systems, basically anything that doesn't involve sitting around contemplating their navels. "Peaceful" types get happy about new colonies, new treaties, etc. and unhappy about wars, enemy ships, other races' (whether enemy or ally) colonies in one of "your" systems, etc. Finally, "Bloodthirsty" types get upset about treaties, new colonies, other races' (whether enemy or ally) colonies in "your" systems and they get happy about wars, destroying enemy ships and colonies, etc.

This is just a small sample of what goes into happiness; read the various "AI_Anger" files (in the AI directory; I think aggressive=bloodthirsty, defensive=peaceful and neutral=neutral) for more information.

And build an Urban Pac. Center in EVERY system (I'm pretty sure it's a system-wide effect, so you don't need one on every planet). If you use the Temporal technology trait, use the "Temporal Vacation Center" instead; if you use the Deeply Religious trait, I think you can use one of the shrines. They may not be better than the Urban Pac. Center, but since you'd be researching the racial technology anyway, it saves you from researching Psychology as well.

At least that's how I play, and my planets stay "Jubiliant" (they're fixing this typo in the next patch - although it's been around since SE3). I find that if I don't build a happiness facility, my populations eventually get less and less happy. Not to mention that conquered races STAY unhappy, and frequently end up rioting.