mIRC is the best IRC client to use. go to http://ircspy.com/, and check out the "guides" section there. There is plenty of help there on how to setup and use mIRC for downloading files. ircspy and packetnews.com are both good search engines for finding files on IRC.
there are hundreds of scripts out there, i'd say mIRC is the best for a beginner to use, but far from the best script.
yeah all around for quick type newbie use, mIRC is probably the best way to go. just the look of some scripts tend to overwhelm people not used to it. if you're going to get into it heavier than just quickie downloading, you'll definately want a quality script though. there's a bunch of scripts available here if you want ot check any out - http://www.hawkee.com/scripts.php?type=script
wow darthnip, I had no clue there were that many apps for IRC! If I ever get beyond the point of just using IRC for the XDCC, I will definately check them out...thanks!