on the classic you have to know the speeds ,but on the NG you have bugs on the speed tape.When the speed approaches the selected flap bug,call for next flap position (up or down). Do not select a lower speed without calling for flap (for ex selecting in the MCP target speed for flap 5 while you are with flaps up).Flap ,then speed and so on.
So,after take-off,at speed greater than V2+15 (white bug) call for 'bug up' ,flap 1,at speed approaching bug 1 ,call for flaps up.After flaps up call for VNAV,then AP ON.