It's pretty quick and easy to run up some napkins, never mind how much cheaper it is than buying them and also the fact that you can make them to your own style and colour scheme. Choose a heavyish cotton or a linen - it's wise to test a little in the washing machine for shrinkage or colour loss. Cut out about 30cm squares and embellish them if you like. I simply machine sewed on some ribbons and ric rac but you could applique, embroider or print a design on either for example.
Next you need to hem it to hide the frayed fabric (and ribbon if using) edges. This is pretty easy with only the corners being a bit tricky. Working with right side down throughout, firstly, snip off a little of each corner (this helps to reduce the bulk when all the edges are folded in). The iron is your friend from here on. Iron the edges in evenly all the way round (I turned the edges about 5mm).
Iron the trimmed corners in by the same depth also. If you are not very confident at machine sewing, then tack (large hand stitches) the hem down to stay in place.
Turn the edges once more (just a little deeper than the last turn, so I went about 7mm). Pay extra attention to the all important corners so they sit together nice and neatly (or as neatly as possible at least!) - you have just made a mitred corner! Again, tack the edges down to secure in place for machine sewing.
Almost there now! Machine sew the hem in place, turning the fabric around at the corners (leaving the needle in the fabric as you do this). Remove any tacking and give a good overall press with the iron.