Want to play the game 'by the book' - forget it! - well okay, here is some stuff that might set you on the right track.

A general resource is this Player's Manual (very much updated from the portal version[1]).
Very useful to understand whats written on forums, this wiki and the UBB is this list of Common Terminology
and then there is all the stuff below (to which you can contribute and edit)

General Guides	Color Guides
Beginner Guidance Portal Startup Guide also: Help EDIT this version! Portal Tutorials Mike Clough's Strategy Guide Researching for dummies	Ascendancy - White DL_Snake's Ascendant Guide Maerlyn Style White Sirhatter’s White Guide
Advanced Guidance Topian Early Ranking	Eradication - Red Alzorath's Eradication Guide Azreal's Red Guide
Game Mechanics Alzorath's FAQ v0.3 Bane's Book of Formulas Favour from Gods Ronin's War Formulas Understanding Stacking	Nether - Black Alzorath's Nether Guide Broke and Butter's Battle Guide DOLZero's Devil Guide Sabre Nether Guide Seraph's Devils Guide The Only Guide to Nether You Will Ever Need
Tools or Calculators Geld Optimizer Applet Lonectzn's Stack Calculator	Phantasm - Blue Alzorath's Phantasm Guide
Other Information	Verdancy - Green Alzorath's Verdant Guide Roxton's Tips for Verdant Simple Verdant Guide Sir Hatter's Green Guide for Apprentice Server Verdant Stacking in UBB Hall of Sages Incomplete: weaver's complete guide to green rushing