Head to Goldenrod City and find the Bike Shop. Head north east of the bike shop, and you'll find a woman inside the house. Make sure Togepi is at the front of your party.
Talk to that woman, and she'll say a particular phrase that will rate your Pokemon's happiness. They are as followed:
'It looks really happy! It must love you a lot.' ~ 250-255
'I get the feeling that it really trusts you.' ~ 200-249
'It's friendly towards you. It looks sort of happy.' ~ 150-199
'It's quite cute.' ~ 100-149
'You should treat it better. It's not used to you.' ~ 50-99
'It doesn't seem to like you at all. It looks mean.' ~ 0-49
According to this link the friendship level for your Togepi to evolve is 220.
Hope I helped. :)