Stopping spam is very difficult. The best way is never to give you details to any company, telesales person, news-group, forum or shopping site, and definitely do not put it on a web page.
However the bigger problem is what to do if you start getting spam.
If the spam attack gets out of control it is usually easier and quicker and simpler to change your Email address.
There are anti-spam programs but they can often delete the wrong Emails and you could find them more a nuisance than a help.