I actually have a fortress with a series of towers in construction. (2 of them are done). Heres the basic setup:
First, build an underground tunnel 2 tiles wide to the place where you want the tower. Make an airlock room (only 1 door going in and 1 going out) and place a door at the entrance and exit for this room. Also make 2 levers after the airlock room. Now dig out a small farm, a small barracks (enough for 4 beds), a dining room, a storage room and a room for workshops. Turn off all dump zones except one in storage room. Make all the stockpiles you need (including a good wood stockpile) and then manually select supplies for dumping (booze, some food, some seeds, wood, and a few hundred metal arrows) and they will all be quantum dumped in your storage room. Then reclaim all the stuff you dumped and when a decent number of haulers come lock the door behind them. I found they tried to bring them back to the original stockpiles if I didn't lock them in. Build your workshops (craftsdwarf workshop, carpenters workshop, butchers workshop along with a tannery, a still and a cook shop). Also build a cage and 2 chains. Assign 2 female animals to the chains (assuming you have loose males elsewhere) and this will allow you to have a meatsource. Also build 2 archery targets somewhere in there.
Now build a staircase to the surface and build your tower with no doors to the outside (don't forget to use fortifications on your shooting level) and then connect each lever to one of the doors on the airlock and remember which one hooks to which. When this is done open both doors and recruit 4 peasants and station them in the tower complex somewhere. You can use 2 peasants and 2 practiced marksdwarves if you want, but I figure they have plenty of time and seclusion to practice.
If you are having trouble getting them all in there at once then just wait for one to get in there, unrecruit him and make him pull the lever for the door on his side. Then station the other 3 in the airlock room and as they get there close the door behind them and open the door to the tower. Remember that you never want a open path to the outside world lest you lose a peasant and have to bring him back. Anyways, once you have your 2 peasants and 2 marksdwarves you should set both peasants to have ALL jobs except mining and wood cutting. They will keep the place self sufficient and the 2 archers can practice all they want. If they run out of practice bolts make some new ones out of wood. If you need beer then brew some up. Make sure to keep your farm going, and keep an eye on seed stocks. If you have 200 of a seed then no more will be generated when the plant is eaten, prepared or brewed. This means your tower could run completely out of seeds while your fortress swims in them. If your tower ever runs out of stocks (or metal arrows) then you can dump some in the airlock room.
I built my 2 towers completely out of green glass so it took a while to complete it, but it should be faster using stone