steaming

I use a plastic spray bottle set on a wide mist spray and spray my loaves jsut as they go into the oven and then spray them again after about 15 minutes - I get a nice, brown, chewy crust that's not too thick.

Steam is effective during the first 5-10 minutes of the bake - too much steam and you might wind up with a soft crust.   Each time you open the oven door, you lose heat.

A few ice cubes can be used to humidify the oven about five minutes or so before you plan to load the bread, but I don't think they are a such a great source of steam. You don't need boiling water - hot water will do just fine.  Dan DiMuzio recently commented on this here.

If you really want to take steaming to the next level, TFL member SteveB created a very impressive steaming method - watch his video here

I haven't tried rigging such a unit yet, but it sure is tempting!

IMHO, the very best way to steam bread is to cover it for the first half of the baking time.  No ice, no hot water, no McGyveresque contraptions. 

The dough has moisture in it and it's usually enough to provide just the amount of steam you need.  If it's a particularly low hydration formula, you can help it along by spritzing your dough with water before covering it, but that's rarely necessary. 

You will be amazed at the results--crisp, crackly crusts and oven spring that will knock your socks off! 

Furthermore, this is a very safe way to do it.  No sputtering and spitting hot water and steam threatening to burn you.  No risk to the glass in your oven door.  No excess moisture to harm to the delicate electronic components of modern fancy ovens. 

You don't need anything fancy or expensive to do it.  You can find a big foil turkey roasting pan at the grocery store or Dollar store. (Check out this page on Artisan Bread in Five Minutes a Day--you don't have to be making their bread for this to work).  As long as the pan is big enough to contain your risen bread and not so big that it is bigger than your stone, you're in business. 

 I got a big oval enamel roasting pan at Goodwill for just a few dollars and it doesn't get all banged up and bent out of shape like the inexpensive foil pan. 

Or you can use something else you might have around the house, as long as it's oven proof AND you can handle it safely when it's very HOT.  Some people use Pyrex bowls and such, but they are very hard to handle when very hot.  So use common sense.  Be careful when taking a hot glass vessel out of the oven--it can shatter if you put it on a very cool or wet surface!

If you want to get fancier, there are options such as clay bakers like La Cloche (a clay baker designed for bread making), Romertopf, and other clay baking vessels, stoneware pans, stock pots (make sure the handles are oven proof), etc. 

It's not as exciting and adrenaline producing as other methods, but it works great. 

Sorry, metropical, regardless of what you read or hear, water cannot turn to steam until it reaches its boiling point.  That's not my fault, it's a fact of science.*  Water will steam more quickly if it's introduced as a fine mist and sprayed into a super heated environment.  But if the spray is too cold and contacts a temperature sensitive surface (e.g. baking stone) the surface that it contacts will often crack.  Many baking stones have been ruined when cold water is sprayed on them in an oven.  As an aside, keep in mind that every time you spray a mist into the hot oven, the temperature of the oven drops dramatically.  It has not choice.  When some of it's heat goes to turn the droplets of water into steam, it's temperature cannot remain constant.

In a container, the vessel must first reach the proper boiling temperature (212 degrees fahrenheit  -  100 degrees celcius  -  at sea level) before the water can attain that temperture.  I know, I know.  You've read and heard a lot from people who are widely experienced in bread baking about generting steam in an oven who claim they know some secret way of producing steam without boiling water.  But it doesn't matter whether you rely on nuclear fission or a camp fire, water will not turn to steam until it reaches 212 fahrenheit at sea level. 

When I use a spray bottle to spritz the loaf in the oven, I make certain the water in the bottle is very warm (like hot)  and I avoid spraying directly onto the loaf so the water doesn't make immediately contact with the stone.

Personally, I often us the technique suggested by janknitz.  It eliminates a lot of guesswork.

*physics -  the laws of thermodynamics

To give credit where due, Susan of San Diego introduced that technique here some time ago.  It's fondly called Susan's Magic Bowl technique and if you do a TFL search using those terms, you'll come across her quite wonderful recipes for a lovely sourdough boule that's baked under the bowl.

I use an inverted disposable aluminum lasagna pan (like $3.00).  Aluminum has a low speicific heat and is very thin, so it heats (and cools) VERY quickly.  This eliminates the need to heat the vessel with the oven.  I put the shaped dough on the stone and invert the lasagna pan over it.  Ten minutes later, take of the pan.  Two minutes later, the pan is cool enough to touch.  Although the pan is disposable, I reuse mine over and over.

Sometimes I spritz the inside of the pan with water to add extra water for evaporation.  However, spritz or no spritz seems to work fine.

-Adam