To me, that's like asking how you meet a celebrity. They could just be doing their groceries at the same store as you, because they're people and need to do that, and maybe they're vacationing in your town while their TV series is on hiatus or something. It could also help if you go to convention panels or autograph signings, but you'd need to know when and where that event would be, how to travel there, if there's an entrance fee, who is really going to be there, and so on. Or you could just run into people who look a lot like a celebrity or, maybe, being influenced by someone influenced by a lesser-known celebrity...have a lot of the same attitude as a result, and then keep you wondering, "Wait, was that just ___ I saw??" But you've got obligations and aren't sure or you're shy and you've already lost sight of them so you don't follow.
This metaphor kind of falls apart if I bring up like a friend of a friend puts up a YouTube video that they didn't expect to go viral, but a parallel question would remain: what is celebrity?
Likewise, what do you mean by "dragon"?
You can do particular meditations to get you astral, and you'll find some very strange things over in the otherworld. A dragon might be one of them, but it might not be exactly as you think; but once you've caught the "style" or the Name of it, then you can call it, and if it doesn't mind you thinking it's a dragon, and you can't think of it as anything but a dragon, then it's probably a dragon. Or you can just go around exploring and ask random people you meet where you can see one.
Like with the grocery store celebrity sighting example, the dragon might already be there. Or like the convention example, you might have to go looking around for the astral garden of Hesperides where Ladon guards the golden apple tree, or find a torii dragon gate, or something.
You meet a dragon is astral travel.You must visualize that you are in a wood and you see a big cave.You enter in it.You see a dragon.Be polite,introduce him.Don't be scared,the dragon will ignore you.If you are nervous is possible to hurt you.You mustn't use a dragon only for his power,he will ignore you.You can give him a gift.
you meet dragons typically by projecting and going to them. like spirits, dragons have been known to wander the earth for a quick visit similar to how we project to the astral. however unlike spirit, you have an incredibly low chance of bumping into one that way. you could try setting up an altar and/or leaving an offering and meditating before it, but this is still a maybe if you haven't already met with them. once you begin working with them, sure, but it's like calling to a god you've never talked to asking for them to appear in front of you right now. it probably won't happen, and if it does, hope they didn't come by just to slap you.
it really doesn't require something special, the ability to project and to see/sense/hear them [one or all] the requirements outside of that is knowing yourself, and having patience, dragons help people who already know stuff, they don't sit down and go 'step one, circle casting' it's like trying to join the Olympic figure skate team when you don't even own skates, you will get thrown out.
Depends on the offering. Incense for instance, light it and say something like 'mighty dragons, please accept this offering of incense.' [It's easier if you know the dragons name.] If you know the Dragon or what a type of Dragon favours [like earth dragons favour gems and crystals] place them in an offering dish and call to the Dragon like last time, only specify Earth Dragon and crystals.