This young man properly sets his feet and body with his
front side facing the target before he fields the bunt.
Probably the biggest tip I try to pass along is the importance of approaching the bunted ball so that the fielder's front side (glove side shoulder, hip, and foot) are pointing towards the target of their eventual throw before they even touch the ball. If the only play will be at first base, the front side is lined up to first. If there is a possibility of getting the lead runner on the play, the fielder would field the ball in a position where his front side faces the base he might be throwing to. This will require the fielder to be a bit quicker with his footwork to align the front side properly. If he approaches the ball assuming the throw is going to the lead base and then hears the catcher yell "One! One!", he will still have time to adjust and make the throw to first base. Adjustments to lead bases after fielding the bunt become more difficult. They take more time and tend to lead to more errors being made. Here’s an example of what I’m talking about.
Say a pitcher is slow getting off the mound, doesn’t get his front side facing the lead base, and fields it with his front side facing first face (usually the case with a right handed pitcher). The catcher then yells “Three! Three!.” Because the pitcher’s front side is not facing third base, he will have to try and shift his attention and front side towards third after he touches the ball. As a result, the throw to third takes longer because of the added footwork after fielding the bunt. The pitcher knows he has to hurry and is more likely to rush his throw. In many cases a late and/or bad throw is made.
If his front side had been facing the base where the lead runner was heading (third base) and the catcher yelled “Three! Three!”, his body would already have been in a position to quickly make the throw to third. If the catcher yelled “One! One!”, he would still have time to shift his feet and his front side to first base and make the throw there. This is because it usually takes longer for the batter to run to first than a runner to go from second to third base. Therefore, both options are covered well but only if he gets to the ball very quickly and sets his feet properly.
As players get older, the speed of the runners and therefore the speed of an entire bunt play become faster. The players who are quicker to get their bodies in the proper position before the bunt is fielded will have the advantage.