I think there are three aspects to a mix - aeration, moisture retention, and organic matter/fertilizer. Perlite is almost always used for aeration because it is cheap. Moisture retention can be vermiculite, peat, or coir. Then the last element is where everyone seems to have their own recipe. Worm castings are probably one of the best ideas, but they are ungodly expensive. I bought some mushroom compost this year that I am going to use - it looks like black dirt, just like worm castings. I think any sort of compost would work; it depends on your budget. I like to mix in a little high-P guano and greensand as slow-working organic fertilizers. I also cheat and use Osmocote, too. (not the high-N, though, read the label) It's a pelleted time-release chemical fert.
My mix this year is going to be 7 parts perlite, 6 parts peat-based pro mix, and 5 parts mushroom compost/organic fertilizers. I also add a little mycogrow from fungi perfecti. I tend to add some sort of fertilizer at every watering, even if it is only a bit of alaskan fish, kelp, molasses, or epsom salt. When the plant is fruiting, I give it some of the two fertilizers I use in the fertilizer injector, calcium nitrate and another that is 4-18-38. Earth Juice sells a high-K organic product called "Meta-K" that would do the same thing for anyone trying to stay organic.
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