When you deplane at MIA you follow everyone else (and the overhead signs) to Immigration/Passport control. Depending on your arrival gate the walk can be long or short. Once you clear Immigration follow everyone else to your left and proceed down the escalators to the Customs Hall. There will be a sign at the bottom of the escalator listing what carrousel your checked luggage will arrive on. Once you claim your bags you simply proceed to the Customs Hall exit. There will be two lines at the exit, one for those who have nothing to declare and one for those who have something to declare. Take the appropriate line. Just to the left outside the Customs Hall exit there is a baggage drop off area for those with connecting flights (regardless of which terminal your connecting flight will be using). A few yards away is the entrance to the TSA checkpoint for your connecting flight. It's all relatively straight forward and everything is well marked with overhead signs.