IMO, unless you have a professional sort of steamer, there's not much you can set up at home to do a great steaming job. Especially if you're cooking a lot of lobster. It just takes too long for the heat to er, bring the lobsters to their demise, and the racket in the pot will drive you out of the kitchen. Boiling is the way to go!
You can season the water, if you like, with some cut up lemons, peppercorns, bay leaf, and Old Bay seasoning. Put that in the water right at the beginning, and by the time the water comes to a boil, you'll have a wonderful broth to cook the critters in.