Some things to consider, more along the subject of container gardening rather than herbs in general.  Medium (whatever you're gonna put in your container to grow your plants in) in a container does NOT work the same way as gardening in the ground, or gardening in raised beds.  I'll try to give you the basics here, but my best advice is to thoroughly read this thread at GardenWeb's Container Gardening forum:  http://forums2.gardenweb.com/f…..64.html?11

I know it may seem like a bit much, but the OP REALLY knows what he's talking about.

So the basics are, there are certain things that always happen when water moves through a medium.  What those things are depend mostly on the size of the particles in a medium, and how the medium is contained.  A key concept to understand is "wicking."  When water "wicks," it is drawn through the medium by capillary action.  If you are gardening in the ground, all the soil surrounding your garden (in effect, all of Mother Earth) functions to "wick" the water from the surface, where you're putting it, down deep to where the roots of your plants are, and beyond.  But if you garden in a container, surrounding your medium with walls, you no longer have the whole Earth to draw your water down through your medium from the top.  So you have to rely on gravity. 

Unfortunately, gravity is a tricky thing.  If the particle size of your medium is very fine, on a very tiny level, the attraction of the water to the particles becomes greater than the pull of gravity, and the water can't move freely through the particles.  This results in "perching," where the water drains through your medium until a certain point, then stops.  In a 10" pot, depending on the size of your medium, this will be somewhere between 1 & 2" from the bottom of your pot.  If you could cut the pot in half from top to bottom, you would literally see a straight line horizontal across the pot about 1" up from the bottom, where above that line the medium is wet, and below it the medium is completely dry.  The old adage about putting gravel or pottery shards in the bottom of your pots to allow for drainage doesn't work, it simply moves that perch line further up from the bottom of the pot.  You'd still see it 1-2" from the bottom of your medium.

You can do an experiment where you take a styrofoam cup, and fill it with the medium you want to use in your container.  Now sprinkle water over it until the medium is soaked.  Then punch a hole in the middle of the bottom of your cup with something, and see how much water runs out.  Then, take something organic (best is like a bamboo skewer), and gently slide it up into the hole until the tip of the skewer reaches the middle area of your cup.  See how much more water runs out?  You've encountered the Perched Water Table (PWT), and allowed the skewer to act as a wick, drawing the water down and through your medium!

So why does all this matter, you ask?  Well, if the water in your container is perching, instead of draining away, it sits in your medium, around the roots of your plants, and literally suffocates/drowns them.  Most herbs (and pretty much any plant that's not aquatic) don't like "wet feet," and if your medium doesn't drain properly, your plants will at the very least, not thrive.  At the worst, they will die.  (I've found this one out the hard way, I'm afraid.)

So how do I keep water from perching in my containers?  There are numerous things you can do, rising in expense & complexity.  The simplest is instead of having a single drainage hole in the bottom of your container, make multiple holes around the perimiter, about 1-2" up from the bottom, depending on the size of your container.  The next simplest is to use the single hole in the bottom of the container, but put a wick through it.  Let the wick extend from the center of your medium to several inches outside the container.  Highest recommended is a strip from a rayon mop, followed by 1/4" diameter cotton rope.  Wicks will only work if the end that is outside of the pot is actually touching Mother Earth.  The most complex, and expensive (relatively speaking), but also the most versatile, is to create a potting mix that has a large enough particle size that it won't let water perch.  I'll let you read for yourself in the Container Gardening thread some of Al's recipes for a mix like this.  Typically they contain Sphagnum Peat, Perlite, and Pine Bark Fines.

I can tell you from personal experience, that this is the best all around solution I've ever found.  I gardened herbs & veggies successfully in containers (ranging from Homer Buckets to whiskey barrels to kiddie wading pools) using these concepts & methods.  Sorry to get so long-winded, but I find it's better to teach principles rather than practices.  :)

It's only necessary if you DON'T use a specially formulated well draining mix for your containers (like Al's 5-1-1 mix).  It's helpful, but if you have a good mix, it's not necessary.  Miracle Gro & a couple others make a potting MIX (not to be confused with potting SOIL), but it, to most accounts, doesn't seem to do as well as a home-made mix like Al's.  See the link above for Al's recipe.

When you go, tell a salesperson exactly what you wish to do.  Ask if they can recommend a good organic potting mix (I think Fox Farms has one).  Make sure to tell them that you don't want moisture control.  Or, if you're up to making your own, buy sphagnum peat, small perlite, pine bark fines (sometimes sold as a soil conditioner, you want pieces that are about 1/4" square) and a small amount of garden lime.  It's not daunting, I promise.  If you get a good quality potting mix, you'll be fine.  :)  The awesome thing about gardening is that if you screw it up, you can always get more plants.  It's a learning process, and we (or at least I) typically learn by making mistakes.  You'll figure out what works for you, and for your plants & the location you're putting them in.  The two best sources of information I can recommend are the Container Gardening & Herbs forums on Gardenweb.