It takes a little mind shift, and might change the way you think about some crochet stitches but it isn't a hard fix.
Here is a typical front post stitch worked around the entire post in the row below rather than working it through the loops.
Usually we think of the crochet stitch as the hole we need to work into, the threads we need to work through. When you work posts, you must count the posts, and pay attention to the hole you work into next.
When you flip your work over, you see the loop running horizontal around the stitch. Its a little hard to see here, but right above that horizontal loop is the top loops of the stitch. I've stuck my hook through to help you see it.
Flip it over and now you see which stitch you should work into. It is to the left of the hook.
When worked, it looks as if it crowds your post stitch a bit, but it isn't.
Its very easy to work the first stitch after the post into the wrong loop, but give this a try. It might help.
If over a sample piece, you find your stitches slanting right, count the number of posts before you work your first post stitch. Is that number right, or do you have one too many posts?
If your sample piece has the post stitches running left, check the hole you are working into.
I strongly recommend Crocheted Aran Sweaters by Jane Snedden Peaver. she explains how to avoid the front post slant in her book very, very well.