How can the novice keeper learn to safely handle venomous snakes? What is the best "first hot" to train with? In my opinion, the best training you can get in safely handling venomous snakes is handling a very wide variety of nonvenomous snakes. The best "first hot" isn't. Some of the most physically challenging snakes to handle are not venomous, and these are the ones that will really help you sharpen your handling skills.
I have handled many species of venomous and nonvenomous snakes, and once you get past the mystique, they are all pretty much just variations on the same basic themes. Snakes that occupy the same environmental niche and have the same body type all tend to handle and behave very similarly. I have found it very effective to teach classes where the students see me working with a real venomous snake, and then they practice the same skill set with a nonvenomous analogue that behaves and handles similarly. The real venomous snake I am using as a demo model is usually easier to handle than the nonvenomous stand-ins.
I have had students complain that my cottonmouth was just sitting there and letting me put a tube on its head while they had to struggle mightily with their water snakes. My cobras are usually much easier to bag than the racers we hand out for student practice, and my mambas are sweethearts compared to Asian rat snakes. It is usually quite obvious in class which snakes are the most physically challenging to handle. It's not the ones with fangs.
There's actually a pretty good evolutionary reason for this. Snakes that evolved to catch their food using pure speed and strength are generally faster and stronger than snakes that rely on venom. Hold a constrictor in your hands and then do the same with a safely head-tubed rattlesnake. Big difference in terms of muscle tone. The rattlesnake is comparatively weak and helpless in your hands, whereas the constrictor can give you a bit of an arm wrestle. The one physical arena in which the viperids at least can equal or exceed their nonvenomous cousins is the sudden and explosive strike. But this is not an effort they can sustain in a struggle with a handler.
Anyone who becomes very competent at moving around a wide variety of belligerent nonvenomous species with hook and tongs has the basic skill set necessary to safely work with venomous species. The physical moves are exactly the same. It is only the consequences that are more serious if you get careless.
Every species and even some individuals will handle a little differently, and you learn to fine-tune your techniques a bit when working with a particular snake or a particular type of snake that reacts and moves a certain way. The best education you can get that will help you fine tune your handling to a particular venomous species is not just working with that single species, but working with a wide variety of species so that there is nothing a snake can do that will really surprise you. To that end I highly recommend working with a wide variety of the worst tempered nonvenomous snakes you can lay a hook on, until your moves are automatic and you can't be surprised by any variation in their behavior.
To be specific, if you want to learn how to handle a particular type of venomous snake, find a nonvenomous snake with a similar body type that lives in the same type of environment. Locate a suitable specimen, preferably one that the seller has unhappily nicknamed "Satan" or "Evil Bastard" or something even less printable. The chances are fairly good that this animal's physical abilities as well as its temper should actually be more impressive than the venomous snake you want to learn how to handle. If you want to be sure that you're getting an animal that really is a pretty good act-alike, inquire on one of the venomous forums like kingsnake.com or Fauna Classifieds where you can get feedback from experienced keepers.
Some people suggest training with a venomoid, a snake that has had its venom glands removed. Aside from the ethical issues around venomoids, this really isn't the best choice. An Asian rat snake makes a better trainer mamba in many ways than a real mamba, and the same can be true for other species that are wickedly fast and strong because they don't have the advantage of venom to kill their food. A large, angry semi-arboreal colubrid simulates a mamba in really tiptop physical shape who is having a very bad scale day, which is a good thing to learn how to deal with.
A lot of bites happen because of complacency. The average venomous snake can be placid or timid so much of the time that a handler can get overconfident, and when that snake finally does get motivated to seriously act out, they aren't prepared to deal with it. Training a new keeper on a snake that will always physically challenge them is better than letting them be surprised when a hot snake suddenly does its thing after being nice and calm for days on end. Along with complacency is losing focus, or letting yourself get distracted by something. Even if you are showing the snake to others and talking about it, you need to be fully focused on the animal and not on all the fun facts and interesting markings. Speaking of focus, although it may seem a little extreme, if you wear glasses and are the type of person who is blind without them, you may want to consider something like Lasik Denver if you are serious about becoming a snake handler. Nothing would be worse than having a squirming "hot" snake on the end of your hook and accidentally knocking your glasses off!
The skill of a handler is not in handling the average venomous snake. The average venomous snake doesn't actually try to bite most of the time (though some species are certainly an exception). The skill of the handler is in his or her ability to deal with the snake that is absolutely freaking out and being defensive or trying to escape to the far reach of its physical ability to do so. That is the specific skill set I want to teach, and I really can teach it best using horrible tempered, fast and agile nonvenomous snakes that are close to a venomous snake in body type.
The average long term captive venomoid snake will not match a healthy wild animal for temper and physical agility in avoiding the handler's control. My mambas are not venomoid, but they are long term captives. When I use them as trainer snakes I am aware that they are probably not going to demonstrate the full physical capabilities of this species because they are habituated to handling. Since I won't let a novice deal with a freshly imported mamba, they get nasty big arboreal colubrids instead that will demonstrate just how far and fast this type of snake can move when it is really motivated to.
It is the behavior that really makes the difference, and a long term captive (which a venomoid would be) is simply not the best training model. Anyone who trains exclusively on long term captive snakes may not be prepared for a "snake emergency" when an animal seriously starts acting out. There are of course some species that retain quite a temper even as long term captives, and they are much more acceptable training animals. But some species habituate and calm down fairly rapidly, or they rarely act out even when they are freshly wild caught. So an act-alike that will more reliably put up a fight is the better trainer.