One way to help determine air speed when landing is to pay attention to your SINK RATE. Assuming the plane is more or less level it will SINK faster the slower it is going (in relation to the wind it is in). A short blip of throttle will move it forward and slow the sink rate.
I teach newbies to make long slow centerline passes and slow em down a bit each pass. Start 15 feet high work down to one. have 'em cut the throttle and OPPS they landed :-)