Fill a large pot halfway with water. Add the beer, 2 tablespoons of Old Bay, pickling spice, and one lemon (halved along with the juice).
Bring the water to a boil.
Add the shrimp.
Cook for 2-4 minutes or until done as desired.
Drain the shrimp in a colander but do not rinse. Sprinkle with more Old Bay as desired and toss gently.
Serve with the remaining lemon (sliced) and cocktail sauce. I serve my shrimp over fresh crushed ice.
Note: I like to cook a single shrimp first. I use it as a test to determine the exact cook time for the remaining shrimp. In my case, my 20 count shrimp took 2 minutes and 40 seconds to be perfect. Shrimp aren't cheap, and you want the best-cooked shrimp. I think it's worth this extra step to determine the ideal cook time!