I don't think there is distinction between shy and bold girls.The distinction is between party girls and librarian types.Many times party girls are more difficult to get.
Among the main types of girls I've come across are:
1) uneducated sexy-but-dodgy looking girls who seem to go exclusively for 'dresiarze' (vulgar addidas-wearing skinhead guys). In Krakow, some ex-pats call such girls 'Hutas' because many of them come from the poor industrial district of Nowa Huta.
2) Confident, classy, slightly more more mature girls who don't often go to clubs. Usually engaged or married.
3) simple, young, often shy and naive 'librarian-type' village girls that frequent the cheap student clubs like Carpe Diem
4) slightly above-average looking party girls with v little personality who go to posher clubs and think they hotter than they are (we just call them 'deluded')
5) Girls who like and hang around exclusively with foreigners. Most of them are rather average in the looks department (not an expression I use, but I've come across the term 'language wh***s')
6) Hippies, freaks, wierdos, bisexuals etc. Can be found in gay-friendly clubs like Kitsch. Unpredictable.
The decent, classy ones are the hardest ones to find, especially if they're single, but those ones are girlfriend-material. The most difficult ones are the Hutas, unless you have a shaven head, look like the Hulk without the green, and can say 'kurwa' after almost every word. The village girls are definitely the easiest to approach but their deep inferiority complexes make you almost feel guilty about shagging them.