The first time it happened I thought I had an 'accident'.

Some things that helped me are:

Being sufficiently hydrated.
Finding that special G spot and giving it some extra special attention.
And just forget about it. If I am anxious it doesn't happen. It is when I forget and just allow myself to experience whatever is being done... stop thinking... it most often happens.

Some people don't squirt. It doesn't make their orgasms better or not and isn't an indication of the level of their arousal. And squirting may be embarrassing if if happens with a partner that doesn't understand it.