Let's start with the most important thing: the drinks. Say you're serving wine, beer and cocktails. Go with a white, a red, a sparkling if you're feeling super-festive (prosecco and cava are great options for affordable bubbles for a crowd), a beer that works nicely with most food (a crisp pilsner does well here) and a signature cocktail or two for the night, ideally something that's easy to mix up in quantity (martinis or manhattans are a good place to start).
Plan on two drinks (of any kind) per person in the first hour, then one drink per hour thereafter. Don't forget to provide nonalcoholic drinks, as well.
Now, let's talk food. There are a couple of categories of cocktail party food — pick a few from each category, and remember you'll probably need about 12 total bites per person (more if your party is during a mealtime). These are, of course, not the only options by a long shot.
If your party's not themed, your best bet is to let the signature cocktail determine the style of the food. Martinis? Think '50s chic, with olives, cheese straws and smoked salmon bruschetta. Whiskey Sours? Try down-home, with pulled-pork sliders and mac 'n' cheese baked in mini muffin tins. Margaritas? Go festive with guacamole and 2-bite tacos.
Take it easy on yourself; there's no need to make everything. Supply at least one store-bought snack:
Dishes that can be cooked in advance and kept warm or served at room temperature:
Dishes that can be assembled ahead of time:
Cook as much as you can in advance. Cut limes, lemons and any other drink garnishes, stock your fridge with ice (8 ounces ice per person is a generous amount for making cocktails and chilling beer and wine) and set up the bar. The bar is best placed at the opposite side of the room from the food to keep people flowing around and eliminate traffic jams.
Two hours out, start chilling white wine and beer, and pull anything to-be-served-at-room-temp out of the fridge. An hour before the party, make the last-minute food items and warm the hot foods in a 175 degree F. oven.
Half an hour before the party starts, pour yourself a drink, stock the bar with ice and put music on. During the party, make the occasional round to replenish ice, hot food and drink garnishes. And don't forget to relax and enjoy your party!