I agree with Susan, if you can get your vivarium set up a couple days before you get the snake if you can.
When I got my snake it was a surprise. I was planning on getting one but so I was getting all the stuff My wife surprised me by asking me to come over and look at the reptiles, she wanted to see what a corn snake was. After looking at them she asked me to hold one thinking I would "creep out" and back out of it (I was afraid of snakes, and until I got my corn I had never held one) but instead Seth was very easy going and pretty relaxed and I really liked him. So she went ahead and told me to get him and he was my Christmas Present. Well, we got hom and I finished getting his tank set up.
I put the heat pad under it, put in a couple of homemade hides with a fake plant. Well we went to walmart later that day and I picked up a thermometer with a probe and hot glued it to the hotside just above the heat pad. Well it was late by the time I put the thermometer in. The next morning I got up and checked ont he snake and almost had a heart attack, it was 135F over the hot spot in his cage!!!! OMG, talk about freak out. So I ran to the hardware store and picked up a dimmer switch and a cheep extension cord and patched the dimmer into the extension cord so I could plug the heat pad into it to adjust the power moving through to adjust the heat. So far that has worked fine for me.
I said all that to say make sure you have some way to regulate the heat pad or you could wind up with a dead snake. Lucky for me mine was a sub-adult and he knew to get away from it but it could have gone the other way around.