The first rule is to always sand in the direction of the grain. Never goes perpendicular.
Second determine how deep the defects are that you want sanded out.
I will always go in this order, use the coarse paper first, to get out the deep blems, sanding uniformily all over not in just one area. This could cause a bowl shape.
Then move to medium, sand out the rought sandpaper marks, then go to fine, then to a 220 grit then to steel wool. Then apply a sanding sealer, then steel wool again.
So, you move from coarse to fine to steel wool. This will make that smooth furniture top look.
Now staining and sealing, go also in the direction of the grain and apply one coat, let dry, lightly wool or buff, then another coat and lightly buff then another. Light coats much better than one heavy coat. A nice piece of furniture might have 15 coats of stain or sealant.
I have a gun stock that has 22 hand rubbed coats of stain and sealant.