We have a .com domain, hosted in the US, that does reasonably well on google in the US. How do we replicate that for google.ca, or other googles, like google.uk? I've heard that you need to be hosted in that country, and also have heard you might be better off building a second website (without duplicate content) using a .ca domain? Any thoughts?
I would just keep focusing on growing your rankings in the US google and adding more and more high quality content to your .com site, but if you really want to rank well in google.ca or .uk, your best bet would probably be to like you said "building a second website (without duplicate content) using a .ca domain" or getting backlinks to your .com site from .uk and .ca sites that rank well.
A website with .ca will be easier to rank well in google.ca but if your business is in Canada you could also use Webmaster Tools to inform Google of this, and they will give better results for google.ca (and possibly lower results for google.com). The hosting location is not important.
subfolders call it ca and use google webmaster tools for geo targeting the subfolders new site sandbox and have to wait to get google trust
Keep on doing normal seo and you will find your website in Google.com ranking. If you want to increase your website ranking in different particular countries than you have to target those countries market to promote your website in google.co, google.uk and so on