Do not open emails with attachments unless you recognize the sender. Even if you recognize the sender be wary of opening the attachment. Was this sent by your friend or was their computer infected with a worm?
Do not open emails from senders you do not recognize.
Do not download images from senders you do not recognize.
Do not open HTML emails from senders you do not recognize. Once you do this the sender will get a hit on their server and then they will know that your email address is valid and they will know the IP address of your computer.
Do not use the preview pane. Using the preview pane is the same as opening the email. To be honest, I do not practice what I preach on this one.
Block Junk Mail. Your Email Server, Email Program, or Anti-Virus Program can be configured to block email from certain senders or that fit certain criteria. The features vary widely so I can not address any specifics here.
Respond to your emails promptly. Your company should set a standard of responding to all customer requests within 48 hours. Then stick to it. If you sell yourself as prompt and courteous then you need to reply to emails, voice mails, and letters within a reasonable amount of time. If you do not have an answer for the client at least respond with an "I will research that and get back to you."
If you do not check your emails often, then do not publicize your email address on your web site. It would be better to simply list your office phone or cell phone.