I don't believe advertisers or other people who have something obvious to gain from lying, and I don't necessarily believe people who are telling me verifiable facts about the world that don't seem to mesh well with what I already know, but I do believe people when they tell me things about themselves. Things like "I'll be there at noon."
It gets me in trouble sometimes.
2. Unspecified "we".
Once upon a time, when I said "We went hiking this weekend," that meant my parents and my sibling and me. These days, it could mean anybody at all (and me), and I'm terrible about remembering to say who was with me when. I'll say things like "We saw Kooza!" and "Then we went off to dinner at Marie Callender's" and never specify who "we" is (seven people in the first instance, five in the second). I'm actually much better about this on LiveJournal than in person or on instant messenger, because I can look back over the post and go "Oh, before I put the funny thing so-and-so said in the last paragraph, I should probably mention that he was there" and go add that helpful background information to the first paragraph.
3. I think everybody knows everything.
Not everybody everybody, but once I've told three or four people about something, some little switch in my brain flicks over to "everybody knows that" and I sort of assume I've told everyone I'd expect to have told. LiveJournal is particularly bad for this, although enough repetitions of "I told you that!" "No you didn't." "But I posted about it on LiveJournal! I must have told you!" have at least trained andres_s_p_b to read the darn thing occasionally. Also, if I have been meaning to tell someone something for long enough that I've planned specific bits of phrasing to use, sometimes I forget whether I actually said it or only thought it.
Recent examples: A friend from TAMS first realized I had a boyfriend more than two years after we started dating. (How many of you knew I went to TAMS?) Today I was amused by a long list of viola jokes, and andres_s_p_b was confused -- "But you've never played violin or viola or cello!" he said. "Yes I have," I said. And yet he complains that he's heard all my stories. Clearly not.
Relatedly, I often mention things in very casual, tangential ways without realizing quite how tangential and casual they actually are. I think I've given someone a brief outline or portion of a situation, with an opportunity to inquire further if they are interested, and the other person doesn't realize there was a situation to be inquired about. (This fed into the friend-didn't-know-about-boyfriend-for-t
4. I expect people to ask questions when they are confused.
I don't know why; they hardly ever do. But for some reason, I still think that when people are confused about something, they'll ask me about it, either when it comes up in conversation or when presented with an opportunity like this one. (If it's important and it's bothering them, I even expect them to bring it up on their own, some time after it's been particularly confusing. This is why I don't usually realize when people are missing fairly basic information; they don't ask about it, so I never twig to the confusion.)
Personally, I don't ask a whole lot of questions. I very much like learning about people, but I'm happy to learn whatever they want to tell me rather than hunting specific pieces of information. Way back when I was in the Puzzle Pirates beta, my mom joined the crew I'd been sailing with for a month or so, and asked everyone all these very basic questions -- "What do you do for a living? How old are you? Where do you live? What's your name?" -- that it had just never occurred to me to ask. I'll ask questions about things as they come up, to keep a conversation going or if something intriguing is mentioned, but I don't tend to produce questions on my own.
I'm not sure if that makes expecting other people to do it weirder or not.