How do you make Pokemon more friendly?

• Give them a Soothe Bell (which can be found behind the gate in the National Park, if you don't have it yet) and walk around with it
• Battle with them often (try not to let it faint)
• Feed them Vitamins like Carbos, Iron, Protein, etc.
• Put them in your PokeWalker
• Keep them in your Party and walk around with them (let them be the first Pokemon in your Party)

Hope this helps!