This is the first time I'll be optimizing a website outside of the states. It is .co.uk - so I'm wondering how do I go about doing this. If he wants to rank high in the states - as far as backlinking is concerned - where should I backlink from? Sites from here (.com, .org, .edu, .etc)? Also - if he wants to rank high in the UK google - do I backlink from sites in the UK? Will backlinking from sites like EZineArticles and Hubpages help?
Yes you need to make links of .co.uk domains. You can also take some other links like .com, .net, .org etc to look natural. -Ishu
You must have relevant links for the domain that are in the same country, so for .co.uk try searching google.co.uk for forums and so some posts with the links in the sigs, then try uk directories, should work. We used these principles and got a .co.uk to #1 on google.co.uk and number 6 on .com for the same search term, now doing with a .com
As other people have said, try and get links from sites in the same country, and also make sure those links are as relevant as possible.
install flagfox and check if the sites are uk regional that way, but more importantly .co.uk links are really easy to get anyway so just target them.