I try to keep these things as sparse as possible.

In my bags I prefer to keep only raiding consumables like flasks, potions, buff food, and drinks of some sort.  I also carry around my “tools” which consists of my Gnomish Utility Knife and my enchanting rod. I carry Jeeves and MOLL-E as well as my Mote Extractor for the occasions when I need to use them as well.  Also my fishing pole!  I try to keep all gear and enchanting materials out of my bag because I frequently disenchant for people and don’t want to get them confused, and I’m the loot distributor in the raid so I disenchant on those occasions too.

In my bag I have the occasional items I’ve come across that are worth keeping like tabards or rewards for achievements or other collector type items.  I have a store of enchanting materials and some materials for engineering as well.  I also keep any gear I might use but don’t have equipped in here just in case.  Generally speaking when a new iLvl comes up out this gets disenchanted.

All of the rest of the materials I come across I ship to my banker who either stores it or sells it on the auction house.