In the context of a relationship I am way more considerate of my partner in the initial stages. So as to feel them out, to get a sense of what they're about, what their boundaries are, etc. This only doesn't work when they aren't just as considerate to you as you are to them. If they do something inconsiderate to me, I'll point it out, and explain it. Communication is necessary IMO in a healthy relationship. If they continue that action, then they are not worth my time. Once we get a sense of how the other is, we can commence the comfortable union!
As far as how I am with my friends I am also considerate, but it's different when they aren't your intimate partner. I always give my friends the light of day to talk, and share; and ask how they're doing etc. With a partner it's a sense of their problems can end up being your problems (their larger, life issues), whereas with a friend if they don't feel like talking about something, then let them do that.