Make sure your tail wheel is lined up with your rudder. I turn on the tx and rx. and roll my fuse on the garage floor. If the rudder is straight, the plane should not veer left or right.
I was ground looping one day and discovered my tailwheel had slipped and was wanting to turn the plane RIGHT when up elevator was applied. (to keep the wheel down on taxi and roll out). The wheel was doing the steering
until the tail came up. Now the LEFT rudder I was appling was not what most planes need on take off to correct for engine torque. As a result I quickly ground looped left
..lownslo........ Bob