First, I have to agree with the comments already posted.  It's all good advice.

I'd like to add that you need to commit completely to the production and the character.  Listen to the director and do what he/she asks, regardless of whether you agree, but also be willing to take chances onstage as an actor.  Do this in rehearsals.  If the director doesn't like it, he'll let you know.  Most directors I know, however, appreciate a little creativity from actors in the production (not performance) stage.

the first time I directed a play I filled the lead part with an actor who up until then had been in one show with about three lines and had only done that as a favor to the director, although he tried to talk me out of giving him the lead, once it was clear my mind was made up he did a wonderful job and it was simply because he made a DECISION to jump in with both feet and give it all he could, when I ran into him recently after about two years I find he is a working actor, and he says people still recognize him in our town from that show! The moral of this ramble is that sometimes if the newbie is willing to commit lack of experience will mean nothing, use the fear to drive you and be a sponge at rehearsals, you'll be fine