I'd do a couple things.
Go to a patterning board (opened up 50 lb dog food sack over a bale of hay has served many times), put a small circle in the middle of it. Go back 30 yards or so, from a low unmounted position, mount the gun and shoot, without aiming. Is the shot pattern centered around where you were looking?
Without shells, stand in your house, garage, barn, yard, wherever. Find a fairly long horizontal line (trimwork on the bedroom ceiling, edge of the barn roof, power line, whatever). Start from a low position, mount the gun as you're swinging down the horizontal line. When you get to a marker (corner, power transformer, Christmas tree topper), pull the trigger as you keep on swinging through it. Lower gun, then go back and do it from the opposite direction. This will get you some muscle memory on mounting the gun, trackingd own a line, and following through after the shot. When I was a kid new to shooting I'd do this dozens of times a night.
Remember, don't aim a shotgun. Point it where the target is going to be. Stay loose. Movement is with the whole body, not just your arms.