For Bon Appetit, writer JJ Goode explores American's misconception of the dish: "Like salsa and mole, guacamole is mistakenly thought of as a particular dish rather than as an expansive culinary category." He goes on to say that essentially anytime an avocado is mixed with other ingredients, it's guacamole. So there's a whole vast world out there, and you've probably had some really delicious versions of the dip and some pretty sub-par ones. He recommends choosing ripe Hass Avocados and allowing them to ripen a little longer than you think you should. Also, don't be afraid of salt, and take it easy on the lime juice.
Kathryn Goldstein, writer for Slate, would agree with Goode's suggestion of allowing avocados to ripen further than you may think necessary. She suggests buying them from the store a few days before you'll use them to give them time to fully ripen. And instead of onions, Goldstein prefers shallots.