multi task! i breed pokemon and hatched them by cycling up and down the cycle road with the pokemon i wanted happiness on was hold a soothe bell. others i recommend are:
-Veilstone, once a day or (clock trick it) get a massage from the lady there, u also get fashion case items.
-take them for a walk in the park at hearthome city, togegi can go, and i think eevee as well. make sure you have the step counter on . every 200 steps turn round and talk to your pokemon to get items..
-Battling, prob the best multitask happiness giver. EXP, EV's, Moves. go to the veilstone dept. store and buy lemonade to heal your pokemon with after battle. it has high happiness value.
Single ways of promoting happiness (unessessary and time consuming)
-give vitamins. takes alot of them, so i recomend battle tower and use the BP gained rather than spend your money.
-Poffins, stupid stupid poffins. i hate poffins and all they stand for. evolving my feebas was a pain. to use poffins for happiness increase u'd have to be a mad man. but plenty still do it.
I recommend battling with lemonade, lol that sound kinda stupid. (always have the soothe bell on your pokemon you wish to bring the happiness up on. it doubles your effort) and also the egg hatching method. esp, if your a fussy breeder. SOOTHE BELL