Apple announced public Beta program for OSX Yosemite last year, but only select few users were able to enroll for the Beta program. This year going forward, Apple announced that both iOS and OSX users, will be able to roll in for the Beta program for iOS 9 and OSX El Capitan starting in July. While it is not clear whether this roll out will be restricted to only certain number of users, we hope that there would be no such restrictions given that no such announcement was made.
So, if you cannot wait for the final release of both the software for your Mac and iPhone/ iPad you can sign up the public beta and help Apple collect the reports so that they can improve upon the bugs before the release goes live. It is worth noting that public Beta will most likely be about 3rd or 4th beta release to developers, and therefore will be stable enough to use in the day to day usage. Add to it, if you install the Public Beta, when the final release is available, you will get the OTA automatically to exit the beta without having to downgrade or play around with the files.
In order to participate in the Beta Program, all you need to do is enroll yourself in the program here. You will have to log into the program by entering your iCloud credentials, post which you will have to accept the Terms & Conditions to be a part. Once the Public Beta is available you will be contacted via an E-Mail so that you will be able to download iOS 9 when it is ready for you.
In case you do not want to install iOS 9, we will be writing about some of the features of iOS 9 that can be brought on iOS 8, like the post on Power Saving Mode right here.