1) Visit the store page of the region you want to purchase the game from (via a trader)
e.g. http://store.steampowered.com/app/298110/?cc=ru
2) Hover over the "Add to cart" button of the package you want and take note of its id
e.g. javascript:addToCart( 54144);
3) Look up the package on SteamDB
e.g. https://steamdb.info/sub/54144/
4) Look out for
AllowCrossRegionTradingAndGifting,
onlyallowrunincountries and (to a lesser extent)
prohibitrunincountries
ACRTAG = Copies sourced from Eastern Europe, South America, South-east Asia or Turkey will be region-locked at the activation level if they're sent to an international user (Eastern European gifts can only be activated by those in Eastern Europe and so on)
OARIC = The game will only run if you're in one of the listed countries
PRIC = The will
not run if you're in one of the listed countries
It's also possible for publishers to "language-lock" region-specific packages, as is the case with Far Cry 4 RU, but this isn't something that can be ascertained using SteamDB until the game has released and the depot names are known; however, publishers are usually pretty good about putting up a warning message on the store page in a timely fashion.