Talking to strangers isn't that difficult really. If you say something dumb, it doesn't matter because in all likelihood you'll never see them again anyway. The trickier part is turning strangers into friends. For that you need regular engagement with the same people, and to get that you need to be bumping into the regularly. So, common interest groups, clubs, meeting places, events, where you can keep seeing the person is necessary. It is possible to get lucky and snag onto a common interest in the first meeting with someone and one might invite the other to an outing involving that interest, but it's not often the case. Appearances obviously play a role too; as you're more likely to get someone to engage with you a second time if you come across as interesting, fun and easy going. The other person can't feel threatened, intimidated, anxious, embarrassed, uncomfortable or repulsed by your presence. Put your best foot forward as they say. It's hard because you can be rejected many, many times, in subtle or direct ways, and to keep trying seems pointless and painful, but really, if we don't want to be lonely, we have to keep trying. And what if tomorrow is the day you met someone that really appeals to you? That possibility, as slight as it may be, should keep you trying.