That's exactly the right use for sticky threads, anallawalla. They'll stay at the top of the page forever. Forums often use them for important announcements, welcomes, forum "charters" (what to post, what not to post), FAQ (to reduce redundant posts), etc.
Having said that, I'd recommend being judicious when using this feature. I don't like sticky posts much, as they shove "real" threads farther down the page. Combine an ample header with four or five sticky posts, and suddenly your members have to scroll down before they can view the real content.
Let me go further than rogerd. One sticky thread is all you normally should have (combine Charter, FAQ, Welcome etc). I suppose an occasional "semi-sticky" thread can be had for an important announcement, but it should soon be "unstuck".