So maybe you don't tank or perhaps have never tanked. Maybe you're new to the game, maybe you just haven't tried it out yet, maybe you used to tank but then stopped for whatever reason and aren't feeling comfortable picking it back up. Whatever your situation, the tanking game in World of Warcraft is available to you as a warrior.
A lot of guides tend to focus on gearing and speccing your warrior to tank, glossing over what you actually do as a tank. What buttons are you hitting and when? Sometimes that's because it seems self evident, or because specific fights call for specific things. This guide is written from an absolutely basic perspective: It will tell you what to do and when to do it, assuming you've no experience at all as a tank. Therefore, this caveat: No guide can make up for practical experience, and you may well learn different ways to perform the role that conflict with this. And that's fine. Learning the role through doing will help teach you what's suited to you; this is just intended to get you started out on that road.
This guide also assumes you are level 85. At least for the first 60 or so levels, you have few enough abilities that there's really no confusion and if you level as a prot warrior, you'll pick this up anyway. This is intended for DPS warriors and PvPers who have never tanked but would like to, as well as old hands who haven't tanked in a while.