I just spend a lot of money screwing things up till I get it right...
Actually I keep lots of notes, make lots of different e-liquids. I then mix the completed e-liquids together in various percentages, say a nice chocolate e-liquid and a nice mint, more mint or more chocolate, it isn't so hard getting the basics, but fine tuning is the most difficult thing in the world to nail down.
By way of example I was vaping a particular flavor I made and got it down to 1/3 of a tank on my genesis, I had to go pick up one of the kids so I grabbed a different flavor to top it off a bit of a swirl and BAM it was like magic...holy crap this is freaking nice. So the 2/3 + 1/3 mixture will become a new flavor for me to work on; with some 9 different flavors used to make it, I'm thinking it will be a fun one for sure.
Mostly though I just screw stuff up, and spend far more money than I should.
Maurice
It's cool when you Stumble on a Killer Combination.
I chased the Perfect Cherry Flavor for about a Year. I got close Many Times by adding a drop or two of Pineapple and a few drops of Strawberry. But never Reach Cherry Nirvana.
In a Very ...... Off moment over a Terrible Experiment with Cherry/White Pear, I wanted the Bottle it was in so I dumped it into a Bottle of Coconut. Which Didn't turn out very good Either.
But I'll be Darned. Cherry/White Grape/Coconut wasn't all that Bad. Not Bad at All.
Funny how the Flavoring Gods Smile on us Once in Awhile.