If your son is interested in playing the game, I would suggest taking him to a local hobby/comics/games shop. usually you can find listings in the phone book, but if you can't you can go to the main site for the game, www.yugioh-card.com, and follow all the links down to the events page. on that page you will find a list of all the stores that run sanctioned tournaments (basically, these stores are recognized as official tournament stores by Konami). find one close to you and next to the store name you should find contact info and a rudimentary schedule of what days of the week and at what times that store runs tournaments. I would suggest that you go with your son the first few times then, depending on how old your son is and the age range of the other players at that store, you can start letting him go on his own. My last suggestion would be to always check prices for the cards on ebay, as well as here, and take about maybe 10% off the values you find to get the amount most people would be willing to pay. And always double check the value of any cards being offered for trade, as some (not all, but some) people who play this game tend to try and undervalue what you have and over value what they have. If you have any more questions, feel free to ask and I will be more than happy to help you, or at least point you in the direction of someone who can.