How to opt in and out from OS X Beta versions

How to opt in

If you enrolled your Mac for Apple Beta program, you can download betas and early releases straight from App Store.

For you to do this, you need to download and install a component called OSXElCapitanPublicBetaAccessUtility.dmg

The only downside to it is you're required to install it on your physical OS X, which can not be the most recommendable course of action on production Macs.

If you don't want this, you can opt out from these updates.

How to opt out

Go to System Preferences/App Store.

Click Change next to "Your computer is setup to receive pre-release software update seeds".

Then select "Do Not Show Pre-release Updates". These updates won't show up again in App Store.

Should you change your mind later on, you need to reinstall the .dmg package.

In fact, after performing that change, App Store options will get modified as shown below:

If you want to test pre-release versions without compromising your production Mac, the best option is, IMHO, to activate this setting in an OS X virtual machine.

This will allow to test betas and early releases and play safe, without exposing to any risk whatsoever.