I do this all the time, for Crafting skills (I find Gathering skills tend to take care of themselves, except for maybe Foraging). You just need a regular calculator and someplace to take some notes:
1) Compute the minimum skill XP to needed reach next level (max - current). Call this value 'T'.
2) Select a "grind item". Find the plain item in your recipe book that yields the most XP for the least amount of gathered mats (purchased mats are irrelevant to this). There are usually only a few "golden recipes" per page that are best. If you are making items requiring mixed mats (WS), or there is there is a clear alternate, pick the one that will benefit the Gathering skill that needs it the most (if you want). You may need to make a few test items to find out what XP each recipe gives. (In the old days when the XP gain was a little random, I would do 10 items or so and compute the average.) Remember that the XP gain for a recipe increases each time you level up, and also to recalculate T after any tests.
Call the XP gain 'X' and the processed mat(s) required per the selected item 'M'.
3) Calculate the number of items needed to level the skill (rounding any fraction up): N = T / X
4) Calculate the total number of processed mats needed: P = N x M
5) Double that for the number of raw mats that need to be gathered, P x 2. Note that you will also need P co-factor mats (coal, wool, sap, etc.).
Gather exactly all that stuff and grind away. Make and vendor the created items to free up space.
Remember to check the the new available daily if you level into it (i.e. into a level that is a multiple of 5) before vendoring your last batch of items, as the grind item is often one of the things needed for the new daily.
Oh, yeah, and I never use crafting pots. Don't have enough storage to justify using them.
(Apologies to those who consider the above obvious.)
Edited by WowRefugee, 10 April 2014 - 04:17.