Some may want to do this from a safety aspect (i don't see the need myself) but -

Yes you can link 2 routers together, depending on what you want to do, you have to plug the cables into the proper port. No crossovers needed. Regular cables work just fine, You could connect from router A LAN port to router B LAN port. You would turn off DHCP on router B, I have not yet heard of anyone being successful going from LAN port to router wan port though in theory it should be possible, if going from LAN to LAN you will need a crossover cable since I don't believe these SOHO routers LAN ports are auto mdx (senses if it needs cross or not and configures itself to work with whatever is provided) - Note DHCP is Dynamic Host Configuration Protocol that assigns IP addresses to client machines, including configuration options such as default gateway, subnet mask, DNS servers, etc, SOHO routers include DHCP servers in them to make configuration easy for PC's using the router to get to the Internet.
If you don't disable the DHCP in the router that's not plugged into the Internet, there would be two DHCP servers, and only one of them would actually configure the computers correctly -- the one that's plugged into the Internet. So to ensure your getting configuration from that router, you disable the DHCP server in the router not plugged into the Internet.

Two router setups are common with wifi. You'd want your "inner network" to be secured (using encryption), and the "outer" network insecure. Guests to your home, or network devices with no or poor security features can use the insecure network. All of your own stuff is safely protected in your inner network.

Also see DMZ, or "demilitarized zone" on wikipedia.