First, the words snake and tasty don't go together. Snake meat in the wilds can be likened to eating a roasted bike innertube, unlike the tender snake meat in a fine Texas restaurant that has marinated in wine sauce overnight. Plus, the sheer amount of bones to sort through in a snake makes for a lengthy meal.
Trying to kill a snake is a last-ditch survival effort and one that I don't recommend unless the situation dictates it due to the risk of snakebite. Food is not a short-term survival priority and many have gone 30-40 days without food in the wilderness.
To answer the first question: It's ideally the non-venomous snakes that a survivor would want to procure. This is best done with what I call the Grady Gaston Method. Grady was a member of a B-24 bomber in WWII that crashed in Australia after returning from a bombing run against the Japanese in New Guinea. He survived over 130 days, most of it solo, while living on snake meat that he obtained by hurtling large rocks on the creatures. By the way, he didn't have the means to make fire so he consumed these raw! In the end, it was his sheer willpower, sense of optimism, and serpentine diet that enabled him to endure one of the most epic tales of survival in recent times.
Beware of rattlesnakes, as they can still bite you after they are dead due to a reflexive action of the nervous system. Lopping the head off, burying it, and then skinning and cleaning the snake are the recommended methods established by the military and used by survivors. Once skinned and cleaned, the meat can be boiled up in a stew with any other tasty tidbits or edible plants or placed on sticks and cooked shish-kebab style over the coals.