If the engine has been shut down, and restarted, do the full run up as for an initial start.
If you have just landed and taxied for another takeoff, without shutting down the engine, I don't think that's necessary.
Always do the full 'Vital Actions' check every time, though. (The one that goes: Trim, Throttle, Prop, Mixture, Mags, Fuel, Flaps, Gauges, Gyros, Hatches, Harnesses, Controls full and free, as appropriate for your aircraft.)
MJ
