I have just bought a Nexus 7, but can't get it to enter recovery mode. I press Power + volume up + volume down and choose "recovery mode" in the lists. The Google logo stays there indefinitely, then the tablet just returns back on normal mode. I haven't rooted the N7.
This is a well-known problem with android operating system. You need to connect your Nexus 7 to computer using USB cable, then do Power + VolumeDown on the tablet to get into recovery mode. Issues fixed.