Biggest mistake we are taught is that you sandpaper along the grain.
Yes, maybe you do as a final finish, but you will never remove a longitudinal toolmark by sanding along it.
Going across the grain diablo fashion on curved surfaces is great for taking out tool marks.
A cork block with sandpaper will help remove ripples, without a block you can just make the ripples worse.
First coat of finish is just to help show the tool marks and generally a good deal of it removed.
Best of all is a big stack of patience and decent light.
Del