Step 1: Halve and peel a ripe avocado
Cut your avocado in half, remove the pit, and gently peel off the skin. If the skin sticks, pare it off with a knife as necessary; take care to keep your avocado half looking sharp as it's going to have to stand up to scrutiny on its own.
Figure 1-2 halves per person, depending on what else you're serving.
Step 2: Concoct fruit syrup
Select any fruit preserves you like, so long as they're a nice color (red looks especially good) and contain chunks. I've had good luck with cherry, raspberry, and red currant.
Dissolve preserves into lemon or lime juice to achieve proper syrup consistency. Lemon juice will give a milder flavor, while the more acidic lime juice will require additional sweetener.
Add your sweetener of choice to taste. I prefer agave nectar because it is mildly flavored, isn't too sweet, has a good syrup consistency, and dissolves easily. You can also use honey, white sugar, brown sugar, or artificial sweeteners if you absolutely must. Molasses would overpower the fruit.
A tiny pinch of salt can help sharpen the flavors.
Step 3: Fill avocados with syrup, and serve
For buffets, arrange filled avocados on a tray with enough of a lip to contain drips. The citrus in the syrup will keep the avocados from oxidizing. Serve with additional syrup on the side.