If you are lucky enough to have parents and/or in-laws to help tackle some of this with you, I would strongly suggest using them for this. They have the best up to date knowledge about all the family 411 that might make or break your guests night. We do of course want everyone to have a great time. Jt and I actually were blessed with having both our mothers arrange our family seating, leaving us only to place a few outlier guests and our own friends. This cut the insanity in half!
Once that is done, get sticky tabbed page markers or cut up post its into strips. Write each guests name a seperate strip and then start sticking them to tables. This allows you to move people around simply by un-sticking and re-sticking them to a new table without a lot of messy crossouts or missing guests (both of which are likely to happen when you do it via computer or paper). Once you have arranged every guest (via sticky post it) you can then make a hard copy list to give to your wedding venue, as well as keep for the writing of the place cards.
Some sites offer seating table arrangement charts via the internet, but they often don't exactly mimic the room and to me, were more confusing and difficult to visualize. It also makes it easy to lose some guests as you are deleting and re-entering them.
For more questions on this time saving, easy method or other seating arrangement tips, email us!