On the missions topic ...
I think people who go long-term or on a long specific kind of mission should be called into that, and not simply decide on their own to do it. Well, for that matter, I think anything major we do should be done only in knowing that God has called you to do it. I'm not talking about small things ... just being helpful to someone isn't something you need God to CALL you to do, I think that falls under the general guidelines in Scripture already. Though He MAY lead you to do something specific at times.
But I have had an interest to participate in short-term trips or helping kinds of things, and I think that is a good way to find out how God works with you. Like a short trip to build a school or something comparable. If a person isn't feeling a particular call, I think doing something like that can help sensitize you to what you might should do. But I don't think a person would be as effective if God is not working with them, if they just decide to be a missionary and head off to do it.
I suspect that really isn't something that people do all that often though.

I would hope they would seek God for guidance before doing that.
As for me ... I tend to find it more of a relationship, long-term thing. I think I discussed that here before. I'm more likely to just get to know people, let them see that I sincerely care about them, help them in whatever ways I can, and if (when) it catches their attention that I might be different than other people, and they WANT to know why, then I can share that with them. They generally already know why, and don't have to ask that question. They get right to the more pointed questions ... that can be harder to answer, LOL.
But just sharing my life, myself, my experiences, over time has proven more effective for me. Maybe I'm chicken too ... I will say that I have gone on the door-to-door thing. Haha, I didn't WANT to do it, but I couldn't get out of it. In that scenario, I can NOT be comfortable confronting people, or pushing people, or using any of those kinds of tactics. I do NOT believe in doing that. Some people do not welcome you, and that's ok. I found a surprising number of people DID want to talk, though, and I often found myself somehow knowing what to say to them, and there are a few that stay in my mind even now, years later. God actually DID work through it ... but I just don't like that approach and don't intend to do that again. Like I said, maybe I'm chicken.
It's amazing though, how when you get to know people, the topic so often comes up. And I'm not the one who has to bring it up. They will so often ask, and I think THAT'S where I belong with anything missions-related. It's a lot of work, if you were only doing it for that purpose (I'm not ... I sincerely am interested in knowing people) ... and even once they ask it tends to be a loonnggg process of them really becoming open and responding to what you say. Usually.
But that's JME. I think some people have real gifts in that area.