Decorate only as much as you like. Candles are easy and go a long way is setting a festive atmosphere. Something that smells good - some cinnamon and cloves in a pot of water does the trick. Use themed towels and such to help decorate. They are easy to "undecorate" too!
Use the dishes you have. Mix and match. Nobody cares. They just care about what is in the dishes. I would love to have coordinating plates and platters, but I don't. Who cares?
Buy pre-made food. Nobody but you knows when it is made from scratch anyway. I usually make a couple of things and buy the rest. There is stuff out there better than I can make anyway!
Go casual. Buffets, snack foods, easy things with a light atmosphere creates relaxation for all involved.
What are some tips you have for saving time? Making things easy? Decorating on the cheap?