Turn on for starting and then off for taxying until the check list requires it for power checks. The period when the electric pump is off confirms that the engine pump is working.
Generally follow the same rule in the air. Use the electric fuel pump for climbing or descending, changing tanks and always use for approach and landing. I also use it for procedures such as steep turns and stalls. Leaving it off for the rest of the time means that you'll pick up on an engine pump failure immediately.
Turning off the fuel pump at 1000 feet doesn't give you many options if you do have a problem. I tend to leave the pump on until top of climb leaving plenty of options if a problem arises.
The fuel pump should also be one of the first things to consider switching on if the engine starts running rough or there is a loss of power in flight.
Also consider when you should have the fuel pump firmly off, such as engine firm on start or take off.
Have a look at the POH. Probably the emergency and normal procedure sections.
I learnt on a 152 and have flown a PA28 since getting my licence and now own a share in one. They're great and you'll love it.