Try incorporating their favorite stuff in their furniture and rooms. Gems, metals, woods, etc. If one of 'em likes Pine, embark with some pine wood, and make that dwarf, a bed and cabinet out of it. If the same dwarf likes emerald, and you happen to mine some out, encrust their favorite cabinet with emerald. Make sure every dwarf has a place to eat with a table and chair, sleeps in a bed(this is a big one), give 'em a coffer or a separate room with a statue in it. Try to keep their workshops away from dwarve's they have a grudge against. example -If they don't like the cook, dont put their room next to the cooks room. Making their rooms bigger can help with happiness, as well as eating well cooked meals, with their favorite foods in it. Waterfall is a big plus, you don't even need a whole falls, just some way to generate mist in a square they'll walk through. If they gain any skill increase, they'll get a happy thought, try to keep them away from corpses, and deposit said corpses in coffins. Seeing constructions like traps and levers, well-designed architecture, all give them happy thoughts.
Also, talking with friends gives them a happy thought. So don't worry about your dwarves socializing.
