significant research and tasting variations against each other, I've concluded that simpler is better. Avocados, a little tomato, a little onion, salt and pepper ... that's it! Herbs, spices, lemon or lime? Anything else, I've found, doesn't really enhance the mix.
Here's the simple procedure I've worked out over the years:
INGREDIENTS: (Yields about 2 cups)
1/2 sweet onion
1/2 fresh tomato
2 ripe avocados
1. Mince the onion very fine, and cut the tomato into small dice (there's no need to peel or seed it). You should have about 1/2 cup (120g) of each.
2. Peel the avocados, remove the seeds, and put the meat in a bowl. Mash it roughly with a fork, stirring in the minced onion and then the tomatoes, adding salt to taste. Don't over-mix - a coarse, textured mash is much more interesting than a smooth puree.
3. ADD-INS: As mentioned in the intro, you're certainly welcome to add lime juice or lemon juice, minced garlic (raw or sweated in a little oil to mellow its flavor), cayenne or hot sauce or chili powder, chopped cilantro, other spices and salsa. But after experimenting a bit and directly comparing batches side-by-side, I've come to the conclusion that the basics are best. Much to my surprise, even a shot of lime juice - a potion that adds a happy snap to almost any dish - seemed to diminish the simple purity and rich, buttery character of the dish.
Spoon it into serving bowls and enjoy with crisp tortilla chips or on the side of a Mexican meal. If you need to make your guacamole in advance, the best way to keep it from discoloring is to press a sheet of Saran Wrap down on its surface, sealing out the air. In my experience, lemon and lime juice do little to deter browning; and the old trick of placing the avocado pit in the bowl does nothing at all.