I go with legendary dining rooms (much easier than you'd think; just carve a bigass room and plop down some tables and chairs, no need to decorate if it's big enough);
Seriously. My old standby was a 16x16 room with 72 tables and chairs for a pop cap of 150, and just being completely dug out with only the first few sets of tables was enough to bump it to legendary. Fully appointed with all the seating arrangements and engravings just made it ridiculous. Then of course, I've got tons and tons of meals, many masterwork, for the dwarves to eat, as well as a huge stockpile of booze that has just about every drink in vanilla, and they're in a near constant state of ecstasy. My new design is a bit bigger at 17x17 with the same number of tables and chairs, but this time with a waterfall in the center which just compounds the happiness.
I have trouble getting the dwarves unhappy. I've never seen a serious tantrum spriral, even under some of the worst tragedies that occured in my forts.
Do try to avoid assigning pets, though: pet losses hurt a lot. I try not to give more than 2 war/hunting dog escorts to any single dwarf. More than that, and they can snap if their beloved pets are slaughtered in an ambush or in battle.
I don't assign pets if I can help it. They can't be butchered or caged at need, and they path around the fort eating up fps if they're not pastured. War beasts to guard dwarves that need to go out of the fort into dangerous terrain are an exception, but the only one.