Use the tachometer, not the speedometer, to shift. When not in a hurry I would shift around 3000-3500 rpm, when 'pushing it' you can shift at higher rpms, as long as you're below 'red line' (and, hopefully, the speed limit). What is red line in your car? If all of this doesn't make sense, find a friend or acquaintance who drives a stick and have them go with you on a drive.
Do remember not to shift too soon, 'lugging' the engine is bad for it. That when you're at a low rpm (say, 1500), and when you push on the gas the car jerks or fails to respond.