Strongly agree with all this, with the possible exception of improving luxuries first. Given how cash-strapped the AI is these days, and how little happiness problems you're going to have until you found additional cities (not relevant for OCC, of course), I've found that improving a few farms before luxuries can be effective, DEPENDING on the map and the AIs I've met. For example, if I've met Spain or Attilla (both seem to be rolling in gold early game, due to wonder discoveries (Spain) and CS bullying (Attila)), then luxuries first makes a lot of sense (e.g., raise gold to buy that granary or worker). At the other extreme, if I'm on a water map and the only AI I've met is sitting there with 6 gold and 2 gpt, then I farm, farm, farm, and improve a lux only when I get to 1 or 2 happiness (or meet more gold-heavy AI). Another exception is salt, which gives 1 additional food when improved.