It will come to you, once you are out there. Hopefully you will get a decent preceptor. Do not be afraid to ask questions, if you do not know something!
Bring your text book with you. Look up any thing you have a question on, before hand. If you still do not understand something, then ask. This shows your preceptor that you are willing to learn, by looking up the info. That is a pet peeve of mine. Students that show up without their text book, then ask a million questions.
Do not try to BS your way through something. If there is something you do not know how to do, speak up and ask to be shown how.
Help out with all aspects of the shift. This means help wash truck, help stock truck and help clean up after a call. DO NOT let them make you do everything, just help the crew out.
Do not inject yourself in a conversation, if you do not know the answer. Sit back, listen and learn.
Most of all have fun and learn as much as you can from the preceptor.
If you have a bad preceptor on your first clinical, speak up to your instructor. I have seen students stay with a bad preceptor, because they are afraid to say anything. All this gets you is a bad taste of EMS and you will learn nothing.