Do your homework. Find out which employers are there and draw up a list of those you definitely want to see.
Be prepared to have a serious conversation about why you want to work for them/want a particular role/what you can offer.
Try to think about useful questions (which are targeted rather than just what is your grad scheme like?)
Take an up-dated CV tailored for the type of role you are looking for (if you are considering a couple of role, prepare more than one rather than just generic). If you are not sure about what it should look like for your career (they can be different) contact your uni careers service to check.
I've just registered to attend a STEM graduate fair next month and realised I have no clue what to expect.
I mean, will I need to take my CV? Do I dress as if I'm going for interviews? Is it deluded of me to expect to leave with contact details from companies with a view to being employed once I've finished my degree?
I just don't want to cock up what could be a great opportunity. I've sacrificed a lot to study and don't want it to be for nothing.