It does depend on what a/c you are in. Look at the POH and work from there. In Cessnas the carb control and throttle can be easily used at the same time, so on go arounds that is what I would recommend. Other types PA28's, robins etc. If you have time, carb heat first and then power. But I must stress that ONLY if you are initiating a g/a before getting any where near the runway.
Usually if you have forgotten to put the carb heat away on finals (can't believe that ever happens!!
) Apply full power and then immediately check if the carb heat is cold or not.
I always (try to) get my students into the habit of thinking about the carb heat whenever they consider power. As stated on another thread, carb heat is a large chunk of power missing especially on C150's with a knackered old Lycoming!