Reverse DNS help please?

Hi all. Could someone please, please explain to me how to do a reverse DNS IP lookup? Here's what I know so far: you take an IP address and reverse it's order. e.g. *2.**.*4.*5 becomes *5.*4.**.*2 Then you tag ".in-addr.arpa" to the end and look up the result somewhere. The question is, where? I've done google searches but that's as far as I get. The normal online IP look-ups I use won't accept an address like *5.*4.**.*2.in-addr.arpa Can someone please point me to somewhere online that will accept such an address and give me the location of an IP? Also, if it's a non-American IP what do you tag on to the end of the reversed IP and where would you go to look that up?

All help/s***estions very welcome.

Thank you!