Ok after re-reading what I wrote before, I think I went into lecture mode a little bit lol.. Let me try to put it in noob language:
SUPER EASIEST DIY METHOD:
Buy premixed PG/VG/NIC solution. Most people start with 18mg (medium to regular smoker level). The only sites I know of that sell the mixes with the nic already in them are ecigexpress (not recommended) and here:
Our Unflavored Smoke Juice (Nic. Juice, Nicotine Juice) - My Freedom Smokes
I have not ever ordered from myfreedomsmokes, but I've heard good things.
Next, you need flavor. You can buy flavor concentrates from 1000 different vendors and get 1000 different results. I recommend these:
Flavor Lab
They are the MOST powerful and utterly tasty flavors I've tasted to date. Your mileage may vary.
Start mixing!
SUPER ALMOST-AS-EASY DIY METHOD
Same as above, but you have far more ordering options (more vendors) if you are willing to split your base, by ordering your PG/NIC base and VG separately. I do this now because that's what wizard sells and I wanted to stick with them for the most possible product. It's just as easy as the super easy DIY, only 1 extra step. When you order, instead of 18mg nic, you order 36mg (or adjust accordingly), because the nic mix is 100%PG. then you order 100% VG in equal amounts. Mix 50/50 and MIX WELL. Then add flavors, etc.. yes, it's THAT easy.
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Now, there's variables: Many flavors are PG based, so they can throw off your pg/vg ratio, and they WILL throw off your nic concentration. For instance, if you:
Mix 50/50/18mg base - 80%
Flavors - 20%
So now your base is 60%PG, 40%VG, and your nic content is Roughly 15-16%. I personally don't let that affect my mixing methods, and still mix to taste until I get it right using those guidelines. I also mix closer to 25% flavor, so again, your mileage may vary. Buying the nic base as 100% PG can make it easy enough to calculate your base back to 50/50 after mixing. This is where these calculators gain more value, of course. The best one I know is:
eJuice Me Up - Best eJuice Calculator NOTE: Please read the how-to FAQ's before using it.. it only takes a minute and will save you tons of frustration and product.
Also, some dessert and fruit flavors may come out "sharp". They also sell Ethyl Maltol liquids that are basically sweetners to smooth out the especially sharp flavors that should be sweet. I found adding 1 drop per 1ml on my licorice blend took it from "really frigging good" to "friggin perfect". It's cheap and easy. Again, it will offset your calculations by a fraction because of the dilution of the base, but really.. who cares if the end product is tasty? I don't!
Important enough to mention: ... Until you work out your favorite recipes, you will NOT always get a good final product. This is DIY 101.. it's experimentation, and not all flavors will work well together, and some you just won't like much or at all. I've mixed every possible flavor with several tobacco bases.. For instance, I found clove worked well for me mixed with 555 tobacco, but the same clove tasted like a soiled .... when mixed with a different tobacco base. all things are subjective.
Steeping: Steeping is simply the post-mixing process, usually best with tobacco flavors in the mixes. It's just letting the mix sit, "air out" (I leave the caps off), and mature a bit. As said in the original DIY topic, if you have a bad mix, NO amount of steeping will make it better. A good mix is a good mix right off the bat, steeping really only makes a good batch even better. I found after 5 days, it's nearly as good as it's going to get.. although long-term 30-60 day steeping can be rewarding for making it even 5% (or whatever) better than that, sometimes.