is there a way for me to place a link on a website so that it won't be included in the google search?

for example, i wish to include a link at the bottom of every website i build. i don;t want someone to be able to search "link:www.domain.com" and the sites appear, like what would happen if i included a normal anchor link.

should i be using a nofollow tag or similar?

Yes you should - you can see more information about this here:

http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=96569

e.g. <a href="www.yourcompany.com" rel="nofollow">Your company name</a>