Visit the email list home page.
In the left navigation bar, click "My membership settings".
After clicking that, you'll see a window like this:
In the window, you can change your email delivery preference to one of the following:
- Each email: Notify me for every new message
- Digest: Up to 25 complete messages are combined into single emails and sent daily.
- Abridged: Summaries of up to 150 messages are combined into single emails and sent daily.
- No email: Messages from the group are not sent.
Most users will choose either "Each email" (usually the default) or the "Digest" option. The "No email" option is appropriate if you never want emails and you'll just view all messages in the Google Groups web page.