First- You'll need some earring post pads found at your local craft store. I found these at Michael's (PS- they're ok for sensitive ears). Also grab backs too.. I personally prefer the clear ones.
Second- Find some cute buttons in the color you want. These came in a package of 75 I believe (Lot's of earrings!!) My sister, Amber, had a pair of button earrings in the 80's.. I think that's why I bought neon colors to recreate them :P
Third- Place a dot of hot glue on the post pad and add your button! Easy as pie! Just be careful not to burn yourself. You can give these bad boys as a present, put them on your adorable little girl or keep them for yourself ;]