Let your guests know what kind of party you're having, especially what kind of clothing style dressy to down-home is expected.
Plan for dietary restrictions (vegetarian, vegan, gluten-free, etc.). Ask when you're issuing invitations. And guests, remember: Let your host know if you have a health issue that limits what you can eat, but understand that the whole party can't be shaped by one guest.
Fill several small platters rather than one big platter. Scatter them around the house to keep people from congregating in one spot. Refrigerate them; whipping out a loaded platter is quicker and less messy than refilling a platter during the party.
Remove a slice: People never want to be the first to take something, whether it's a slice of cake or wedge of cheese.
Think in levels when you arrange a buffet or dessert table. Use upside-down vases or cake tiers to put food at different heights. Lifting things adds visual interest and it makes some things easier to pick up if they're above the table surface.
For dramatic displays of single foods, such as deviled eggs or single-bite tarts, wash and dry uncooked beans and use them to fill a platter.
If you're a guest, remember that flowers are nice but not if your host has to drop everything to find a vase. Bring the flowers arranged in a vase, or take them by as a thank-you the next day.