If you can do so, I would highly recommend that you shoot the rabbit targets in sporting clays for a while until you are comfortable with leading crossing targets. In a clays round, there are two rabbit clays that are on the ground and crossing. Because they are on the ground, you can see where your pellets hit and quickly adjust to the lead and follow through. There is nothing like seeing your shot pattern hit the dirt to give you instant feedback. The second best thing is to have a buddy launch crossing clay pidgeons from the side until you get the lead down. Finally, once you get it down, it is good to hunt doves early in the season to get your hunting reaction down. Nearly half of dove shots are crossing at high speed (Nearly as fast as ducks and geese). If you get to the point where you can comfortably hit crossing doves, you will have no trouble with pheasants, quail, geese and ducks. The one caution is to use the same lead with geese... because of their larger size, they appear to be flying slower than they actually are and people tend to erroneously back off on the lead and miss. This type of practice will train you in leading so you have the confidence you need for hunting... good luck!

Are you following through? Maybe you stop swinging when/right before you squezze the trigger that is a common problem on passers. I grabbed a box of cheap shells and just mounted the shotgun swing and keep moving while squezing, with no target, just practice helped alot. You can do the same thing with a snap cap and a mini maglight in the barrell.

i used to point right at them when they are going by but I have found that its better to aim just ahead of them.

Swing past the birds and follow through.