Population planning is one of those things you have to take into account, I think, whenever you're expanding your empire. Starting with your home planet, it already has a population bonus, so using a farm on it will only decrease it's happiness. When I first started playing I had the problem MrVegetable described, where morale seriously declines after a planet reaches a certain population. I tried to get all my planets to the highest population I could. I realized eventually that power comes from the number of planets, not their sizes. Having said that, you need population to grow your tax revenues. I've found the best strategy is to build one farm and one entertainment building on each planet of moderate quality (over 10). Research the next technologies at various points, and then upgrade your farms and morale buildings. This allows you to gain bigger populations and offset the morale effects without wasting more tiles. NEVER build more than one farm though. That's just playin it dangerous! Any thoughts on planning your growth?

Here's the homeworld I've used so far in my no-Colony-rush games:

If I have a Rare Elements or Precursor Mine:

1 Factory on bonus tile.
else
2 Factories.

If I have a Precursor Artifact or Precursor Library:

1 Lab.
else
3 Labs.

The rest is all Economic buildings, topped off with an Economic Capital. Eventually I build a Counter Espionage Center and Spin Control Center. The Factory/s eventually become Manufacturing Centers and the Lab/s eventually become Neutrality Learning Centers or Discovery Spheres. If the above bonus tiles do exist, I'll also drop in a Research Coordination Center and/or Antimatter->Quantum Powerplant.

Like in real life