Tennis: eyes on ball then court in forward part of stroke before contact.
Hockey: eyes on puck then net in forward part of slap shot before contact.
Soccer: eyes on ball then goal in forward part of shot before contact.
Golf: eyes on ball then forward just before contact.
Pool: eyes on cueball then object ball in forward part of stroke before contact. Can also be on the backswing, might change depending on the shot.
Anyway absolutely do not just look at the cueball when stroking...if you need to look at the cueball to hit the right spot on the cueball, then work on your fundamentals. Also hitting the right exact spot on the cueball is not as important as every tries to say it is...much more important to see the table, to judge weight for the position you want...to feel the shot. You can't feel the shot staring at the cueball.