Do it, preferably through the LFD.
If you're casually tanking your weekly wipes together with your equally casual guild mates, you need to see how other people are doing things. Other people include the horribly bad as well.
Not only will you gain insight in how things should be done, but you'll also learn the route to disaster. As an added bonus you'll end up a better tank, because having to react to random shenanigans from your fellow randoms teaches you how fight mechanics interact with a number of players (in this case five) just happening to be located in the direct vincinity of mobs doing bad stuff to you.
You'll also see how different combinations of specs work together, or in some cases fail to work together. By failing I'm not referring to bad resources behind the keyboard, but rather to how some combinations simply carry lackluster synergies.
So, get out there and pug.