I have used Ackis for some time for BS, LW and will for my alts working Tailoring and Enchanting once they move out of the starting recipes.
Once you download the addon a SCAN button will appear on the top right-hand side of the tradeskill panel when you open it up (ex: open up LW and the SCAN button will be on the top of the LW panel).
Simply click on the SCAN button and it will provide a list of recipes (plans, patterns, etc.) you currently do not have (that it does know about) and some information on the recipes that you do not have.
The information is color-coded, e.g., gray for recipes below your current level (if I recall) and I believe red for cross-faction based recipes or for those that you cannot learn (such as Tribal LW patterns for a Dragonscale LW). There may be other colors (going on memory here as I'm not at my gaming PC).
If you hover the cursor over the recipes listed it will provide more detail such as the mob, dungeon or faction you need rep for to get it. It doesn't really provide enough detailed information usually to go get the missing item.
I also use RecipeRadar which shows vendors you are near (via gold dot on the map) that may sell an item that you do not have yet and other information as I recall.
In addition, I use AtlasLoot - so if I know which dungeon I can get a recipe in I can figure out pretty quickly which boss or location in the instance to target to get the item.
If all else fails I refer to this site, wowhead, thottbot, etc.
Basically, Ackis gives you a starting point to know what to look for. I've cross-referenced the scanned list against the list on this site and Ackis seems to have a solid, up-to-date list of everything I've not yet picked up.