I have a question thats been puzzling me for a while now. How do we know (in the real world) how many cables in an etherchannel we need between our routers or switches and even between servers?
Also do we ever have to install 4 NICs on a server to support 4 cables going into our switch forming an etherchannel? Is that even possible?
You should have some bandwidth utilization estimates in order to properly size links. If you have no pre-existing data to go from, then make the best estimate you can based on what type of traffic is anticipated to traverse the network links.
Regarding your 4 port etherchannel question, yes you can configure NIC teaming to include 4 ports on a server. The specific steps in NIC teaming (sometimes called interface bonding) depends on the operating system with which you are working.
Here's a link to a technet blog on NIC Teaming in Windows: http://blogs.technet.com/b/josebda/archive/2010/09/03/using-the-multiple...
And here's a handy video on NIC bonding in Ubuntu Linux: