WhoIs

Here is a short list of Whois lookup tools that you can use, we recommend having a play with them and use the one which you're most comfortable with:

ICANN
DSAK
Internic
Who.Is
GoDadddy
UltraTools.com
Domain Tools
WhoIs.net
WhoIs.sc
DNS Query
Whoismydomain.eu/
DNS Stuff
Domain Dossier
EasyWhoIs.com
TCP IP Utils