Originally Posted by J Miller

Raise the presser foot. Put a thin straight edge against the feed dogs with them all the way up as high as they will go. Now lower the presser foot and sight down the side of it. Does the side of the presser foot align with the ruler? It probably wont. If it doesn't the presser foot shaft will have to aligned to make the foot and feed dogs line up.

I actually use two stainless steel thin straight edge rulers to do this.
Aligning the foot with the feed dogs has corrected about 90% of those machines that feed crooked.

Also make sure there is nothing dragging on your fabric on the left side of the machine. That can affect the way it feeds too.

Joe