The Jinn do not ''grant wishes'' any more than other spirits do.
And the three wishes thing is also fairly new of a concept.
So who/what are the jinn? Well, put simply the Jinn are a variety of tribes of human-like spirits. Their magic is usually quick and dirty.
As for how to contact them, you'll find a variety of instructions in a variety of different places. If you thought the ceremonialism of Western magicians was a bit ''much'', the Muslim magi actually made giant iron circles before summoning jinn, and made sure it was big enough for them in case they fainted.
However, to meet a Jinn, an easier road than the ''say its name 2412412541 times'' would be to simply ask an ally to introduce you to one, or go look for one on the astral plane yourself.