don't think a spell could backfire that badly. you could get hurt yes, might even wind up in the hospital, but i don't think die.
there's articles and forums already here explaining energy work and spell casting, but just sit quietly, while meditating, feel the energy enter your body when you inhale, and leave when you exhale. there's other ways to do this, you could dance, jump, drum, sing, chant, so on.
when you figure out the best method for yourself to charge energy, then try focusing. i suggest candle magic, those teach the basics of casting, and if they backfire, it's not that bad. get a candle of a corresponding colour for the spell you're casting [green=money purple=psychic ability] first charge with energy, then when you feel ready, light the candle. as the flame burns down, focus on your desired outcome. think about all the positive that will come from the spell, and how it will help you. let the candle burn out. if you decide to resume it later, snuff out the flame, don't blow it out, it apparently undoes the spell or blows away some of the energy.
if you don't feel comfortable, you should not cast a spell, it's more likely to backfire if you're afraid, or think it will.