Drinks. Find out what your guests prefer to drink and cater to their tastes. There's absolutely no point in spending a fortune on an expensive bottle of red wine or the finest champagne, only to be told "But I only drink beer" (or alcopops).
If you have the time, tempt your guests with cocktails and mixed drinks before dinner. Serve snacks and nibbles with the drinks, so that people are ravenous before they get to the table.
Make sure you have plenty of soft drinks, chilling in the fridge - at least some of your guests are likely to be driving home afterwards. In any case, drinking water as well as wine is good for you - put out separate glasses for each of these. Offer both still and sparkling bottled water, orange juice and perhaps a caffinated cola drink.
Have an "Assistant Host". Even with the the best preperation, cooking for a dinner party will require you to spend some time in the kitchen, concentrating on the cooking. So what you need is a spouse, partner or just a close friend, who makes sure your guests are looked after - glasses topped up, and so on - while you are attending to the food. Then you can focus on the finishing touches in the kitchen and whisk out your wonderful food to general acclamation.