I borrowed and condensed these tips from this thread:
What is your best tip for new comers

Also I am assembling a list of common Acroyms that New folks might not know so if you have some post them and I will try to keep them organized here

Terms, Abbreviations and Acronyms from D2 - By Thyiad - not all applicable but there is alot of useful terms here.

IGG - In game gold
WTB - Want to buy
WTS - Want to sell
FT - For trade (or sometimes fast trade)
ISO - In search of
OP - original Poster , or sometime Overpriced.