The main thing to note is that i am concentrating on the iOS side of things. Currently Apple has two major betas on the boil, iOS and the new OSX Mavericks, or SeaLion as some people like to call it. I cannot do justice to both so working full on with one.
Betas can be obtained and installed on the black market but there seems little point as there is not a lot you can do and nothing officially.If you are just curios, like leading edge stuff then ok, but if you are going to d any serious work then no point.
You really need to join the development process at Apple which costs £60 per annum, one for iOS and one for OSX, this give you access to all the betas and all the documentation and videos etc. Once you have signed up and signed in you can download the software and any other material you want. Although it is time consuming there are a lot of videos, especially from the recent WWDC that are worth watching to get up to speed.
Anyway, once the beta has downloaded, it’s a DMG you need to run it to open up the package. These will open up as an xxx.ipsw file ready to install.
A question to ask is which device are you going to install to? If you only have your phone then the that may be your only choice but the beta may trash your phone and you will also be upgrading to the new beta’s as they come out. My solution was to buy an iPod touch 5th gen, 32Gb. Then backup my iPhone and restore the iPhone to the iPod. Yes you can do that. Remember though when you restore the backup to hold down the alt/option keys. You then use the ipsw file you have downloaded and unpacked.
Your new device will need registering with Apple through your developer program pages. I would suggest that when you have restored you iPhone backup to the iPod but before you upgrade to the iOS7 beta that you register it. Then do the software upgrade. I didn’t and had to jump through a few hoops to get there.
The software should upgrade in 20 to 30 minutes but adding all the apps may take longer and i would suggest plugging the device into the Mac rather than doing the upgrading by wifi.