Ouderkerk can easily be reached by bike from Amsterdam, just cycle south-east along the river Amstel.
Public transport from Amsterdam: bus 300 from station Amsterdam Bijlmer Arena.
You can also take bus 300 from Schiphol, Haarlem or Amstelveen (Amstelveen busstation or station Oranjebaan of the subway 51 in Amstelveen, direction Amsterdam Bijlmer).
You can combine Ouderkerk aan de Amstel with a visit to
Amstelveen, which has e.g. the
Cobra Museum and the biggest
shopping center in the region. Take bus 300 from Ouderkerk aan de Amstel, direction Haarlem, to the bus station in Amstelveen.