Read several issues of the gaming magazine that you're interested in writing for. While reading, see if you can pick up on what the magazine writing style is, and any particular editorial slant that the magazine tends to conform to. Learn the magazine inside and out to better your chances for writing for it.
Consult the magazine writers guidelines, which may be available on the magazines website, or they could be listed in a writers market reference book. The guidelines will give detailed information on how to send your work, or query for work. Follow the magazine's guidelines specifically on how to properly contact, query, or submit a story.
Send out query letters to multiple gaming magazines that you're interested in writing for. This will better your chances for success and approval. Many magazine editors prefer query letters prior to receiving articles written on spec.
Call the magazine editor that you want to write for if this type of contact preferred. Many magazines do not prefer to receive phone queries, but some do, and a courteous phone call is always more personal than an email or letter.