Combine shrimp together with the lemon (or lime juice), minced garlic and salt and pepper, to taste.
If using raw shrimp: fry in a hot pan until cooked through (about 2-3 minutes per side). Transfer to a salad bowl. If using pre-cooked shrimp: you can do the first step right in the salad bowl. No need to cook them again.
Add the avocados, onion, tomatoes, jalapeños and red peppers (if using). Drizzle with the lemon (or lime) juice, olive oil (If using), cilantro (or parsley), salt cumin and pepper.
Toss gently until evenly mixed through. For a creamier guac, continue mixing until reaching your desired consistency. For a mashed guac, feel free to smash the avocado with a fork, until reaching desired texture. (When doing this, we like to leave some avocado chunks in there.)
Taste and season with extra salt if needed, or an extra squeeze of lemon juice. Serve immediately with chips or veggie sticks for dipping.