You always want your anchor text to be the keywords your targeting, and mixing them up between a couple different variations is always a good idea.
As for PR, high PR links are great, but I like to make sure that everything looks natural, meaning if you buy a bunch of high PR links to a brand new site, that looks strange. Start out buying a blog commenting package and social bookmarking package to get things rolling. After a hundred or so links (or a few weeks), buy a few high quality, high PR links where you can get them. Keep building the medium quality links at the same time though. Slow and steady is a good way to go, if you're trying to SEO for long term and not just a flash in the pan site.
Nofollow, dofollow, high quality, medium quality. You'll want a little of all of these to keep it looking natural. Too heavy on any one of these aspects will not be good for your link building campaign. You can hire all of this out, but make sure they're doing it right and you do it in the right order. Good luck to you.
