I'm always impressed at the skill of some miniature painters who are able to paint a mini that's fully glued on the base. Angel Giraldez, in particular comes to mind... and with the amazing level of quality he's able to achieve, basing a mini before painting is clearly a workable approach for some painters. But for me, I need a bit more flexibility to get my brush in tight areas and so have always mounted my minis on a cork while painting.
Initially, I just grabbed any old cork and pinned a miniature to one end. However, this can get a bit wobbly and unstable. The technique needed improving so I thought I'd write a post about my new and improved "corking" technique.
The first step in this process is to choose the right wine. I like a good cotes de Rhone for fantasy, chianti or possibly montepulciano for sci fi and Rioja for steampunk but your tastes may vary. Actually, it's handy to throw a champagne or prosecco in there every once in a while to get a bigger cork for those minis with wider stances.
Mounting the mini on the cork should be very easy if you've already pinned the legs. Usually I don't find I need any glue, but if things get wobbly I use either a bit of sticky tack (blu tack or a similar brand) or possibly a bit of superglue. It might mean getting out the hobby knife when removing the painted mini from the cork, but that's usually not such a big deal.
All of the above is pretty standard stuff, though. My real quick tip is this: superglue a washer to the base of the cork. Not only does this add weight to the bottom, making it less top-heavy once you've mounted your mini on top, but it also makes it significantly more stable and less likely to wobble or fall over. To bring wobble down to zero, I also push a tiny bit of sticky tack in the hole in the washer. That way it can stick to my paint station and still sit flat. Since I move my paint station around all the time, this has proved invaluable!