Got this old chair and some pale pink velvet from my boyfriends dad. Thought about letting a professional reupholster it, but then decided to do it myself.
Take an old chair.
Remove seat cushion.
..and remove old nails
and old fabric.
Keep the old stuffing (unless you're up to some more work).
place seat cushion on the new fabric
Cut fabric - the new upholstery should be a bit bigger than the old so allow a couple of extra centimeters
Drape the fabric around the seat. Make sure there's excess fabric on all sides and in the corner
When hammering the nails the fabric should be tightly draped around the seat to avoid creases.
Cut off excess fabric.
Place on chair.
Admire your new chair.