You'll frequently see guys at our club rolling their tail draggers down a slight hill on the pavement to see how it tracks.

Everyone adjusts the plane so there is a slight rightward tendancy as it rolls... say about 1 foot for every 12 or so travelled.

This helps compensate a bit for yaw.

If the plane you are trying to fly has a hard yaw at run up you may have to mix a bit of rudder to the throttle to help... normally LESS than 8% rudder to throttle.

Also turn DOWN your expo rates if you have them high on the rudder.

If you have Expo turned up, there is a tendancy to overcorrect as the plane yaws at runup.... normally no more than 15% expo is needed on the rudder.

Finally make sure that both of your front tires toe in a bit. Both should toe-in about 2 degrees ot help reduce yaw during takeoff.