Bandwidth Delay Product Calculation / TCP Window Size tuning

I am attempting some tuning of a windows network, with a 2 MB Wan link. There are quite a few documents on the subject with quite an array of advice, but not much depth. Specifically, I understand how to compute the Bandwidth*Delay Product, but I am not clear as to what to do with that number at that point. I see recommendations that it be adjusted to the nearst MSS, but I am not sure how to determine the MSS value, can someone point me in the right direction?