1. Cook the Pasta (10-12 minutes):
* Bring a large pot of salted water to a rolling boil.
* Add the pasta and cook according to package directions until al dente (tender but still slightly firm to the bite).
* Drain the pasta well and rinse immediately with cold water to stop the cooking process and cool it down. This also helps prevent the pasta from sticking together. Drain thoroughly again.

2. Prepare the Seafood (5-10 minutes, if not using pre-cooked):
* If using raw shrimp, cook them by poaching in simmering water for 2-3 minutes until pink and opaque, or by sautéing or grilling. Let them cool completely, then peel, devein, and remove tails if not already done. If the shrimp are large, cut them into bite-sized pieces (halves or thirds).
* If using imitation crab, flake it or chop it into bite-sized pieces. If using fresh or canned crab, ensure it’s picked over for any shells and flaked.

3. Prepare the Vegetables (10 minutes):
* While the pasta is cooking or cooling, chop all your vegetables: finely dice the celery, red bell pepper, yellow/orange bell pepper, and red onion.
* If using, halve cherry tomatoes or dice cucumber. Rinse capers if adding.
* If you prefer a milder red onion flavor, soak the diced red onion in a small bowl of cold water for 10-15 minutes, then drain well.

4. Make the Lemon-Dill Dressing (5 minutes):
* In a small bowl or a jar with a lid, whisk together the olive oil, fresh lemon juice, Dijon mustard, chopped fresh dill, chopped fresh parsley (if using), and minced garlic (if using).
* Season with salt, black pepper, and a pinch of sugar or honey (if desired to balance the acidity).
* Whisk or shake vigorously until the dressing is well emulsified. Taste and adjust seasonings as needed (more lemon for tang, more salt/pepper, etc.).

5. Combine the Salad (5 minutes):
* In a large mixing bowl, combine the cooled and drained pasta, prepared shrimp, crab meat, diced celery, diced bell peppers, and diced red onion (and any other optional vegetable additions).
* Pour about two-thirds of the Lemon-Dill dressing over the salad ingredients.
* Gently toss everything together until well combined and all ingredients are lightly coated with the dressing. Be careful not to overmix, especially if using delicate real crab meat.

6. Chill and Serve (Minimum 30 minutes, up to a few hours):
* Cover the bowl with plastic wrap and refrigerate the seafood pasta salad for at least 30 minutes before serving. This allows the flavors to meld and the salad to chill thoroughly. It can be made up to 4-6 hours in advance.
* Before serving, give the salad another gentle toss. If it seems a bit dry (pasta can absorb dressing as it sits), add some of the reserved dressing and toss again.
* Garnish with extra fresh dill or parsley, and perhaps a few lemon wedges on the side. Serve chilled.