-то: a great little intensifying, attention-directing, intimacy-creating particle
A few months ago, before this newspaper's online comments section turned into a troll free-for-all and the kindest post that my columns got was, "Stupid expats can't speak Russian anyway, jerk-head," a thoughtful and curious poster asked about the particle -то, which can be added to words, especially pronouns, usually as an intensifier. I love readers' questions, even though they always turn out to be trickier to answer than I expect.
With -то, there are two tricks: figuring out how to use it in daily speech, and then figuring out how to translate it. These two little letters draw attention to a word, intensify the meaning, or add some emotional color to a phrase or utterance — that is, they do what Russian is great at doing. The problem is: English — not so much.
But some usages of -то aren't hard to deal with. First, there's the "I don't know exactly" -то. The particle -то can be added to adverbs like когда (when) or где (where) to produce "some" adverbs: когда-то (sometime), где-то (somewhere), почему-то (for some reason), что-то (something). Все традиции когда-то возникают впервые. (All traditions appear for the first time at some point.) Кто-то мне говорил, что он работает в Питере. (Someone told me that he's working in St. Pete.) In all these cases, the -то means that you know something was done by someone sometime somewhere, but you don't know the specifics.
Then there's the "it's not important" -то. In this case, you add -то to words, usually pronouns, to indicate that although you might know the details, you're not interested in them. For example: Он стал рассказывать: был там-то и там-то, делал то-то и то-то, встречался с теми-то и теми-то. (And he began to tell his story: He was here and there, he did this and that, he met with so-and-so and so-and-so.)
And there's the opposite: the "this is really important" -то. In this case, you add -то to whatever word you want to emphasize or draw attention to.
In spoken language, the -то usually gets conveyed by intonation. Он-то понимает! (***He*** understands.) But it's harder to convey on paper. Usually you have to add a lot to make up for those clever two letters: Слушать-то он слушал, а ничего не понимал. (He might have listened, but it didn't make any difference, he didn't understand a thing.)
Собаку-то он выгулял, но вот дверь закрыть забыл. (He forgot to close the door, but the dog — he sure remembered to walk that dog.) Говорит, что свободных столиков нет, а я-то вижу их полно! (He tells me that there aren't any free tables, but I'm standing there, looking at a lot of them!)
Sometimes the emphasis is hard to grasp. For example, I asked some native speakers to tell me the difference between the phrases "В общем, он хороший человек" and "В общем-то, он хороший человек." Both mean: In general, he's a good person. But since "в общем" means "by and large, not entirely," when -то is added to it, the phrase emphasizes "not entirely" and sounds slightly more doubtful. You expect to hear: но … (but …).
And finally, there's the "emotional" -то. When added to some words, -то somehow conveys intimacy or compassion or warmth. Ой, беда-то! (Oh, my heavens! That's just so sad!) Внучка-то уже читает! (My smart little granddaughter already can read!)
Как тяжело-то! (Man, this is hard!)