What are the most prominent features of Yamagata-ben? I'll be visiting Yamagata City soon and would like to ask: * as an armchair linguist what features of the local dialect to look out for? * what are some common words, phrases, pronunciation differences that I could try to effect to make a nice impression on the locals?

I can't help you with first-hand knowledge, but you can start by looking here. Some of the comparisons (like instead of ) seems to be part of the standard Touhoku-ben fare.

## Edit

According to the Wikipedia article, there's some good variety for the expression I quoted () in its formal version (which is equivalent to ). In Murayama, for instance, it would be ,or, while in Shinjou it would be or . I can't find many explanations in that article, but it seems like quite a variety.