Well I don't know if many big law firms are to active for 1L's and you have a whole other semester to go up or down. In regards to the specific question you should look at NALP to look for the firms your interested in and what they require http://www.nalp.org/
there is the link you may already know about it, but it lists salaries, class rank requirements etc.
With that said welcome to law school I am sure on the first day everybody was convinced they were going to be Valedictorian or at the very least in the top 10% of the class. However, 100% of people can't be in the top 10% and not everyone gets a job in Big Law. It is good to know what you want, but very few people actually end up in Big Law and I know plenty that did who were absolutely miserable at Cravath, O'Melveny, and other big firms. Plenty of people love working at those firms as well, but if your goal is to just get rich then law is not the best way to go about it.
I guess what I am trying to figure out is what about Big Law is so appealing. What firm are you interest in? Why are you interested in it? If you have solid reasons for wanting to work at X firm and are attending Duke Law you have a decent chance of doing it, but if you are solely seeking Big Law for money then you might be disappointed.