Anyone an expert on Maine Coons out there?

We'll be getting a kitty soon and although I've read the breed standards etc it's still quite confusing to determine what a kitten will be like once he grows up...

We're really interested in a silver tabby boy right now and he looks very cute except to my untrained eye he seems a bit on the slender side and his head is a little big. He was born May 18th.
I realise this is an extremely vague description but my question is basically, what should I be looking for in a kitten aside from the obvious health signs etc?

Thanks!

Are you looking for show or pet quality maine coons. MC's take several years to fully develop and young MC's will have more of a slendar build. Males will be heavier then females.