I have a flat bar hybrid.

[markharry66]

Every time I get a flat once I remove the back wheel it never seems to run true.
I am never sure if the wheel is buckled or I am not putting it back in position correctly.
Seems to run as though its buckled.

 

[markharry66]

Quick release. Had been running fine up until last night when had a puncture.

 

[Ajax Bay]

it never seems to run true.
I am never sure if the wheel is buckled

If it's buckled you will see it wobbling from side to side and one or both brake blocks will probably rub. If this is the case the wheel will need truing.
Look at the gap between the chain stays and the tyre. Is there less one side than the other? Are these distances consistent? If no - it's buckled or the tyre sidewall is bulging - check tyre. If 'yes' you may not have seated the axle completely into the dropout slots. A further clue may be whether you can see marks on the dropout round one part of the quick release nut perimeter. Reseat the axle in the correct position, tighten the QR and enjoy the ride.