If you have a pokemon that relies on happiness to evolve (happiny/riolu/togepi ect.) or not the ones that hatch out of an egg will start at level 1 so all of the pokemons stats will be a thier lowest all you need to do is give it berries that make the pokemon more friendly but reduce its base stats but because of the hatched pokemon's low stats it make just makes it friendlier

ALSO: it wont make it fully happy it'll just give you a head start if you want to make it happier go to the massage lady in veistone or goto the department store and buy it items (zinc/carbos/protien/HP UP ect.)grow it to level 5 (with exp share) and train it while holding the soothe bell.there you go it will evolve sooner and learn better moves quicker. simple!