The best flavor is achieved using "real" boiling water from a kettle on a stove. The microwave isually leads to a flatter flavor.
This method, however, is for making the tea when no kettle nor stove are available (i.e. at the office), but use the right tools if you have them and skip the microwave part.
Get a good black tea. This one is Heredia, an organic tea brand from Argentina, but the Twinings English Breakfast Tea would do just as good.
Have a cup filled 2/3 with boiling water, so you leave enough space for the milk. If you have a kettle use it, I don't so I just use the microwave.
It's important not to overheat the water or any other liquids on a microwave oven. They could "explode" leading to burns, given that boiling occurs differently using a microwave.
In my case, I put the cup on the outer region of the spinning plate, which causes bubbles while boiling as a consecuence of the movement of the cup.
This looks half empty but it's actually half full :)
Steep the tea for about three or four minutes. Be careful not to steep longer than five minutes or you'll end up having a bitter tea.
You could also put the teabag in the cup before microwaving to save you some time. I usually don't since this leads to a bitter tasting brew.
Meanwhile, go and get the milk from the fridge. You might want to heat it a little so it is at least at room temperature. Also, for a creamier texture, use whole milk. Here I'm using non fat milk.
After pouring the milk on the tea, add some sugar to taste. It's not requiered (I almost never use sugar on tea) but a little sugar won't kill you (unless you're diabetic)
Enjoy your tea, whether as a replacement for the morning coffee, to complement you breakfast, reading a book or updating you status on twitter while taking a break.