Growls are like, the only thing I can make, I can't make wubs for crap xD
The following steps are using the plugin; "Massive".
Basically, I just use chrome (spectrum, bend + or bend -) and gentle speech (spectrum) and two a bit of mix and match between those 4 oscs, to get different sounds, and put a performer on the wt pos, and the intensities (more on the performer itself later)
I then throw a hardclipper on for extra distortion, and for FX, have a dimension expander and one of the tubes, for moar distortion
I usually don't touch the noise of the feedback, but it's you choice I guess
Anyway, I'll then move on the the filters, have it on parallel, and have scream and double notch filters, try to get it somewhere in between where you like it. Modulate cut off on both filters (how much is up to you) and tweak resonance and such to you liking.
You can use the performer to modulate the EQ too, and pretty much anything you want (I try to modulate as much as possible for that nice growly complex sound)
And then, on the performer, basically go crazy

Make crazy shapes with the curves so your growls sound unique and complex
Usually I will have the x cross fade thingy Iforgotwhatit'scalled only on one performer track channel thingy, but for more complex growls, you could try to incorporate two performer modulations.
http://dl.dropbox.com/u/50449358/maybedrop.wavThis link shows some of my growly stuff, I use them a bit more as wubs there though
http://dl.dropbox.com/u/50449358/StormParty.wavThis one shows me using them more as growls, but when I was making this, I accidentally exported it as really low quality and the mixing is terrible so sorry about that xD
That's just what I do though
The best way is to learn by trial and error (I actually learned how to make a growl on accident without any tutorials xD) and try to be creative so you can make your sounds be unique

Hope I helped!