This writeup will not teach you the mechanics of handling a venomous snake. It will teach you the theory and forethought that comes with snake handling, but this is not a replacement for training under a licensed, competent herpetologist. Understand that by attempting to handle any venomous species without training or supervision by a competent second party, you risk serious injury and possibly death.
There are two steps that come before handling a venomous snake. These are proper understanding of tools, and proper understanding of behavior. I will not discuss the actual act of handling a venomous snake, as it is both highly subjective, and techniques change from handler to handler. Only under the supervision of a competent herpetologist can you learn actual handling techniques.
The first step is to know your tools. You will need a very sturdy hook, the length of which is entirely dependent on the specimen you are handling. For most species, 60" is the minimum. You will also need a pair of tongs, puncture resistant gloves, snakeproof boots, and various snakebags and bagging devices. Also useful are pin sticks, high sided buckets, but these are generally not necessary. Discussion of tools is beyond this article; you can find many resources for researching this equipment. All necessary snake handling tools can be purchased from Midwest Tongs, my personal favorite supplier.
Absolutely necessary for handling any venomous snake is an envenomation protocol. This is a document that includes pertinent information to hand over to emergency medical technicians in the unfortunate event that you are envenomated by a snake you are handling. It should include the latin name and various common names for the species, high resolution color photographs of the specimen, symptoms of envenomation, typical effects and duration of effects, treatment protocols, and the contact information of anyone you work with who is competent to treat snakebites, either domestic or exotic. The number of emergency room staff who are unable to competently treat snakebites, even with native species, is astounding. When you are envenomated by a snake you own, your proper care is your own responsibility. Trust no doctors.
The second step in handling a venomous reptile is to know what you are dealing with. All species have different behavioral characteristics, this is something that can only be learned by observation and experience. North American Viperids, for example, tend to be more docile when hooked than say, Elapid species. Dendroaspis are extremely quick and unpredictable, while Bitis are usually more subdued. Observations on this subject can be very subjective and do change from specimen to specimen, but proper observation is critical to handling any species successfully.
Everything that follows these two steps is, for the most part, common sense. Knowing both your tools and the behavior of your specimen, with proper training you can react to any situation that may arise with whatever species you are handling.
I'm going to close here, as the actual act of snake handling is beyond the scope of a text article. It is something that can only be learned in person, not from reading an article or watching a video. The theory that precedes makes an interesting anthropological read, which is why I presented it only to close at such a dramatic juncture.
It's important to note that before I close I'm not talking about snake handling for showmanship or anything of that sort. I'm speaking solely of handling a specimen for husbandry purposes necessary to the health of the animal.
NOTE 3/8/2011 9:44PM EST: It was suggested to me that this article is a bit sparse, and my desire to not discuss the physical mechanics of snake handling will keep it that way. Thus, I have re-listed from how-to to essay.