how to best shot

The question needs to be reconsidered - 'best shot' needs to be more descriptive.
Similar shot type is called as Super Shot.
In swipe control mode, you can play the Super Shot by swiping two fingers instead of one just as normally as you would hit a regular shot. A Super Shot can only be played/executed if the player's concentration gauge is shining or flashing after getting filled completely. Super Shot doesn't mean the opponent cannot return it unless it is smartly executed.

Sometimes Super Shot may feel a bit unreal. Simply if you would use it in return of a perfectly executed drop shot and you are late in position, reaching at the very last moment before it hits the ground, the executed Super Shot looks completely unrealistic.

Note : Super Shot has not been seen worked with slice shot. If you swipe downwards in either direction (normal swipe action for slice shots) using two fingers, a topspin shot is executed instead of slice shot. Meanwhile if you have switched to any of the pad controls (in-game virtual pad options) you usually have a purple colored virtual button on the bottom right side of the screen while playing a match.

Best Shot (Simple): Depends on point construction or proper gameplay.

Whichever shot you used to win your match should be close to your best shot. Just keep searching.