Okay, well a good combination is Soothe Bell + Luxury Ball. (If you haven't caught the Pokemon yet, do it with a Luxury Ball. :3) You can get the Soothe Bell from Cheryl in Eterna Forest. This should be noted - I can't understand it (lol xD) but you can read it.
Note that holding a Soothe Bell will apply a multiplier of 1.5 (rounding down) to only positive changes and that use of Luxury Balls will not reduce the effects of negative changes.
Firstly, I tell you that using herbs will reduce your friendship, so don't use them.
Otherwise, click here to tell you all the ways to make your Pokemon happy. :3
Hope I helped. :)
Source: Above Link