The key to deads, and I'm sure b fold will have some great hints to add, is to keep your hips low throughout the lift. When you grab the bar, drop your hips as low as you can get them, and concentrate on not letting them rise up while performing the rep, otherwise it turns into more of a stiff legged deadlift. If you keep your head up, and look either straight ahead or up, it'll help keep your back straight which in turn will keep the stress off your lower spine. But you're right, it is much easier to have someone show you how to do it in person.