A well known favorite on the West Coast, this cut is still a butchers secret in our area.  The Tri-Tip is lean and flavorful, with the ability to cook like a steak (seared and sliced thinly) or slow roasted at a low temperature (crockpot or oven) for beef that shreds like a pork roast.  If using the crockpot, rub generously with your favorite spices, add about 1/4-1/2 cup of liquid (water, wine, beer), then cook on low for 8-10 hours before shredding with a fork.  A BBQ dry rub followed by a Carolina vinegar based BBQ sauce works really well.  See below for a recipe suggestion:

Dry rub (makes plenty..store extra in jar):  

1/2 C Smoked Paprika, 1/4 C Brown or Maple Sugar, 1/4 C Garlic Powder, 1 TBL Ground Black Pepper, 3 TBL Sea Salt, 1 TBL Chili Powder, 1 TBL Onion Powder, 1 1/2 TBL Ground Ginger, 2 TSP Ground Rosemary

Carolina Vinegar BBQ Sauce:  

1 C Raw Apple Cider Vinegar, 1 TBL Sea Salt, 1/2 tsp Cayenne Pepper, 1 tsp Crushed Red Pepper Flakes, 1 TBL Brown Sugar