Just to add to all the great info already:

Once your about to enter your snakes enclosure you notcie he is hissing and in strike mode correct? One of the ways you can take him out of strike mode that I found helpful is have a spray bottle on hand. Spray it above the snake a couple times and then let it rain down on him if you will. This will completely change his mind about striking because what he/she thought was about to happen just took a completely different turn and has since put you back in control