If you're a registered developer with Apple you can now jump into the Developer Portal and grab the first beta of iOS 6 as well as the Xcode 4.5 developer preview.
As of now all downloads appear to be going smoothly but you if you have issues downloading the beta, keep in mind Apple's servers are probably going to get slammed pretty quickly.
As with every beta, keep in mind it's only meant for developers. Selling your developer slots to unauthorized users goes against Apple's developer agreement and your license could be suspended indefinitely if you are caught selling your slots.
We also advise against our readers and members of the general public buying slots. This is a perfect time to get scammed or have your credit card information stolen. Scammers are aware that people are out there who want to gain access to the beta and they're fully willing to take advantage of that.
Betas are typically full of lots of bugs and aren't meant to be run on anything but test devices. Installing a beta could cause many issues and could even render many apps, or even worse, your entire device useless. We can't caution enough that if you aren't a developer, it's best to stay away from beta versions of iOS.