Delta3MM -
Frankfurt Hbf to Frankfurt Marriott is very easy - just take the tram in front of the train station. You'll want to get on the tram that goes towards Festhalle/Messe. When you see that stop, the stop right after that one will drop you right in front of the Frankfurt Marriott - a big bargain, especially, since it's 1.15 Euro. A cab/taxi ain't so bad either - around 5-6 euros, but the tram is pretty convenient.
Just walk outside the Hbf, get on the tram that heads to the left (I think it's either tram 15 or tram 16), and get off right after the Festhalle/Messe station. The Frankfurt Marriott is right across the street to your right. If you want to do the U-Bahn/Subway, just get off at Festhalle/Messe, but you'll do some more walking vs. doing the tram which is across the street (I'd say 1-2 blocks more). The U-bahn lie is U4 in the direction of Bockenheimer Warte but if you do either of these, you should be all set.
The tram number is based on my memory, so please verify first since it's been over a year since my FRA trip.
[This message has been edited by HankAAFlyer (edited Jan 19, 2004).]