Wait a Day to Install an Update
You don't need to start your OS X El Capitan download as soon as Apple releases the upgrade. In fact, it is a good idea to wait a few hours if you want to avoid any initial installation hassles and slow downloads.
We typically see a surge in demand for the first several hours of a major release that can lead to very slow downloads and it can easily frustrate users.
If you don't want to deal with any of that, you can simply wait to download OS X El Capitan until later.
With smaller updates this wait can help you avoid any issues that Apple missed, since any big problems will generate a lot of discussion in the first day.