First of all, if you already get spam, don't reply, open or unsubscribe to suspicious mails because that way spammers can track that you still use the emailadress.  If you use Microsoft Outlook Express then you get a preview of the message by default, this also count's as reading.  The hidden images with a size of 1 by 1 pixel will be loaded and they carry your emailadress in their url and that way they can see if you've read the email.  To disable the default preview you go to 'View' > 'Layout' and clear the checkbox at 'Preview Panel' (if you have the inbox open), that way you hide the preview panel and you have to doubleclick on the mail to open it, hell of a good way to prevent them from tracking you.  Unless you open it :) .

 Another thing you can do after that is making the emails bounce, if you go to www.mailwasher.net you can download a program which you can use to check if there is spam in your mailbox.  If so then you can let the program reply with a fake bounce message, some spammer's software reacts on this and removes you from their list.

 A big source of spam are Chain Emails, like funny pictures and so on, and also the fake virusannouncements and charity mails, also the mails which say that if you forward the message you get a mobile phone or so are fake.  Those such things does not really exist, nothing is for free.  If you forward there are a lot of emailaddresses in the body, along with the message you forward them to the next, lets say 10, persons.  If they send it to 10 people each, the email has been sent sent already to 100 people, with the emailadresses in the body, imagine if the mail gets forwarded as few as 10 times how many persons would see the emailadresses.  And not everybody on the net means as good as you, they filter these emailaddresses out and sell them to advertising company's, and they are the source of the spam, or unsolicited mail.  So to prevent the emailadresses to get in the body you put them in the BCC field instead of the To field.  If you do that the destinationadresses are not available to the recipient.  and if he/she forwards the mail it also isn't to the next thousand recipients.  In Hotmail it is easy, there the field Bcc is visible by default, but in Microsoft Outlook Express it isn't.  To get it visible you click on the 'To' label and add the recipients to the Bcc field there by clicking on the 'BCC -->' button.  If your recipients are not in your adressbook you can add anyone you like and click on 'OK' and then the field is visible, after that you can delete this person in the Bcc field and start adding the recipients by hand.  You can split the recipients by using a ; (semicolon).