We get asked this question all the time, by the curious and by those wishing to promote traffic to their airfields, so I thought this could be a good place to put in a detailed answer.
The probably less helpful ways we decide are: prior knowledge of tourist hot spots (e.g. Rothenburg ob der Tauber), geographic location - river, sea, lake and mountain locations generally mean either beautiful scenery or often very old town centre, e.g. Albi, Annecy, Skaanes Fagerhult.
Now what you really want to know is which websites do I refer to:
I think the Danish based
ultralight market website has the best listing, with links to airfields recommended by other aviators. There are many other interesting sections on ultralight market's website (trip reports, links to organisations, rules and regulations etc.) The link provided above is to the Nordic countries listing, there are listings for
everywhere else in the world too though.
For Germany I rely on Angela's
co-pilot's guide, which is a subjective guide, which is what we want.
For Austria I go with
aviator.at
For Switzerland I trust Nelly
And the
Hungarian listing (once google translate has done its magic) is a really good tool as well.
For France
Alasdair Arthur has done a great job
I have also been known to look at the UNESCO world heritage city listing and then search for the nearest airfields.
I also go on flying forums (Flyer, the German Flyer, the Italian forum) and read trip reports, making notes. Aerokurier magazine has excellent trip reports as well.