A simple but very important precaution it to set your email program to open mail as text only. HTML mail (with pictures, logos etc) can have links embedded alerting the sender that you have opened the mail, verifying your email address as active without you doing anything other than open it. - If you must use HTML email at least disable any preview windows so you can delete any mail from untrusted sources before they are opened.

Register a domain name (if you don't want a web site any one will do - .co.uk, .me.uk, etc) and use different email addresses within the domain when signing up for information on web sites etc. That way you can see who sold your email address on to the spammers. Use private domain registration where possible, to avoid the spammers picking up your address from the registration.

Use bcc when forwarding anything to more than one person - then even if they pass it on there's no huge list of email addresses available to a spammer.

Check the headers of a spam email to see what IP address it came from - this can be checked to the source service provider, and if it's a legitimate one you may be able to report the spammer under the service provider's terms of service - see anatomy of an email

Keep lists of spammers IP addresses - use IP address range blocking if you have it available - with this you can block all mail from third world countries where a lot of spam originates, and block dodgy service providers in any country.

Use white lists (lists of preferred email senders which also get filtered on other criteria) and gold lists (lists of email senders that will pass through any other filtering you may have in place) - assuming of course your email provider supports them.

Set up any filtering available - most email providers have at least basic filtering.

Get an email account with a good provider which offers configurable filtering - contact us for free advice.

Respond to a spam email, even with a blank email. Chances are the address is invalid anyway so it won't go anywhere, but sometimes they will use someone else's address, and your response is making you into a spammer. In the unlikely event the spammer used a genuine email address you're instantly a verified active email address to be sold on to other spammers.

Click on any link in a spam email, or any other email you're not absolutely sure of the source. Some emails are deliberately made to look like official emails from banks, PayPal etc, and it is possible to disguise the actual address of the link.

Use your main email address to sign up for anything unless you're sure of the site's reliability. Once in the spammer's databases you have no way of getting it out.

Forward any of those "forward this email to everyone in your address book or the world will end" (hoax) emails or chain letters - however important the source appears to be, or how apparently valid the good cause.

Send bulk mailings (advertising a meeting etc) using all the addresses in the to or cc fields - only ever use bcc (blind copy) so each recipient only sees their own address.

Keep lists of spammer's email addresses - they are all made up or using other people's addresses so you're wasting your time.

Post your main email address on any web site or forum. It will be "harvested" by the spammers' robots and added to their mailing lists.

IT Safe - UK Government site
http://www.itsafe.gov.uk/

Spam Cop - Spam reporting organisation

http://www.spamcop.net