What I do is another flavor with tobacco in the carto. Say fill your carto with tobacco, then add a couple drops of other flavor and see how it tastes.
This is an interesting approach, and I hit upon this quite by accident.
I went a bit overboard on flavourings when I started vaping and mixing - and now when I look at all my bottles of flavouring I just feel overwhelmed, where to start, where to start?
But I thought I should at least mix a few non-tobacco liquids, just to try what that is like. So I did a few days ago, one Mint and one Orange (can't tell you the manufacturer unfortunately, these are from twojliquid.pl who do sell Flavourart's tobacco flavours, and says their other flavours are also of "Italian origin", but
here say these aren't Flavourart, but mixed in Poland from Italian and German ingredients.)
The recommended dilution of these flavours are 10-15 drops per 10ml, which I took to mean 5% and upwards (if 1 drp=1/20 ml then 1 drp/ml would be 5%). So I mixed 10ml at 5% flavouring.
So I tasted these in my dripping atty and thought "hmm, mja-eh, nice, but... perhaps, don't really know if I want to fill up a clean new carto with either of these... "
But then I looked at my already used cartos, a few top-ups away from needing a good boiling. And a clearomizer filled with a commercial liquid that had been OK-ish as zero nic, but turned horrible when cut 50/50 with nic (very weird, cutting it brought out this yucky perfumy-soapy scent and taste). So I thought, these are already either bad or close to being too dirty, why not add a little bit of this orange to that one and little bit of mint to this one?
(I had also just filtered and diluted my first experiment in extracting something from tobacco, so that went into these too.)
Of course when you do this, you will not get a consistent flavour from your carto (and even less from the clearomizer, weirdly enough). What you will get is a rough idea of how the flavours work together. Something to file away for further refinement later - I am now convinced I will at some point try to do a tobacco mix with some orange in it, something I would probably not have thought of if not for this sloppy experimenting.
(When I was really wet behind the ears and had just got my stuff I foolishly thought I could experiment with batches as small as 1ml = an eGo-T tank... Not a good idea. Definitely not.)