Pouring boiling water in a hot pan scares me. As does dripping water on my oven door. I have neither the nerve nor the steadiness of hand required.
I have found a simple technique that works for me.
I can put 150mL of water in a pan on the lower shelf of our oven before preheating to 350F and the steam will last for about the first 15 minutes of baking. I determined the amount of water with several calibration runs with different amounts of water. About 2 minutes after the water evaporates the steam is gone. I can detect the presence of steam by the way the LCD touch panel fogs up when I open the door.
We have a GE Profile electric oven with a "steam clean" feature we have never used. Steam clean is like the usual self-cleaning oven feature except you put water in the bottom of the oven before cleaning. I reasoned that the oven must be capable of holding steam for such a feature to work.
This trick may not work for everyone but I thought it would be worth sharing.
Gary
I have tried using a pan pre-filled with water. It didn't result in as good a bake as throwing water into the steam pan. When I throw the water in the pan I get a huge billow of steam that tries to get out the oven door and vents. That billow also condenses onto the loaf and makes the surface shiny. I don't seem to get that same effect with the pre-filled pan.
I am cautious when I toss in the water. I use about 12oz of water in a 2-cup Pyrex measuring cup. I wear an oven mitt on the hand holding the cup, stand to the side, pull my head away from the opening, and toss the water in with a quick motion.
In 15 or so years of doing this I have not gotten scalded, so I feel comfortable doing it. When I tried the recommendation you sometimes see to spray water into the oven after loading the bread, that's when I almost got burned. The hot air streams out of the oven when you open the door and carries out the mist you just sprayed in, heating it on the way. Aside from being a hazard, the steam didn't help the bread bake better.
TomP
Steaming is entirely about your oven. If you have a vented gas oven it does not matter what you do - boiling water, towels, rocks, cold pan, ice cubes - it's not going to hold steam long enough to matter. On the other end of the spectrum basic electric open element oven with good seal will hold steam so well that it almost does not matter how you steam, everything is going to work.
I've probably been lucky. My previous gas oven and my current electric oven, which is quite vented, act much the same. Billows of steam improve the bread but not as much as I'd like.