First deck (Lazav, Dimir Mastermind), help appreciated!

Hey guys! I recently got into EDH, and built my first deck. I'd appreciate any constructive criticism y'all could give!

http://tappedout.net/mtg-decks/lazav-v1/

I'm considering dropping a couple of creature counters for...something else. I'd also like to swap out a few more basic lands for mana rocks, but I'm not real sure where to go from here. Again, any tips and pointers are appreciated!