You can always try swirling a drop of flavoring in about an ounce of water to get an idea of how it will taste. I usually use plain seltzer for this, though I also flavor my own seltzer with my flavorings too.
I usually try out testers immediately after mixing them, just giving them a really good shake (before I got all my fancy lab equipment) and then trying them on an RBA. I take initial impressions, because somethings are quite awesome shake and vape (in fact I prefer some flavors fresh over having been steeped.) Then after 24 hours I take another taste, then at 3 days, then at 1 week, then once a week after that until the bottle is gone…taking notes on the different flavor perceptions I get from the flavor and how it changes with steeping.
After a week I usually mix up a couple more tests of that flavor at different percentages, higher and or lower based on my 1 week analysis. If it was too strong I do two tests at lower percentages, if it was too weak, I’d try higher percentages. I do however continue to test the original sample bottle each week, along with the other percentages of that flavor. Being impatient I usually mix up a recipe or two with that flavor after I’ve had a taste, so that it can start steeping as well.
Since I’ve been doing this long enough, I can usually tell out of the bottle if I’m going to like something or not. If I get serious off flavors (the ones listed on the Devils Wheel of flavors-- google it for a copy of the wheel) out of the bottle, there is a good chance that there will be off flavors in the finished juice. But that doesn’t always mean that the flavoring is of no use, as sometimes those off flavors can be masked, or at low enough percentages won’t be percievable. And some flavors in the end just need a really good long steep (upwards of 3 months or more) before they are an awesome flavor.
I usually test flavors out in 10ml bottles, but lately I’ve just been doing up 30mls for the ease of it with my equipment. I’ve got a crap-ton of bottles partially vaped and still steeping all around me on my worktops. But I can tell you that your notes will be your gold in mixing, especially as you accumlate more flavorings. Give yourself good notes to work off of, even if you’re the only person who could read and understand them, that’s all you need. Because when you make an amazing juice that may have been meh when you first mixed it, and you pull it out of your steeping cabinet, or find it hiding behind your microwave (I just did that tonight) you’ll want to know you have the recipe and your notes. You’d think I’d learn this and follow my own advice, but I am sitting here vaping a bottle labeled Strawberry Melon Kiwi, that I think I mixed up about 3 months ago, and I didn’t like it at first, now it’s delicious and I’m hoping I can find the recipe I used for it! doh lol
Welcome to the mixing adventure.