Is is possible to get a high PR with a Blogger.com blog? If you can, how? Submit to directories, advertise, etc.?
It isn't any harder or easier to get PR on a blogger.com site. PR is determined by sites that link to your site. Without incoming links, you'll get no PR. Google is in the middle of a crack down on directories and paid links - you should have a site that has content that people/sites will naturally want to link to. I would personally forget about PR unless you are trying to sell links.
I agree with mjewel unless your want to sell links PR is not important, it's just a merry go round game, people buy PR links so they will get PR so people will buy PR links so they can get people to buy PR links from them so they can get PR so people will buy PR links from them to get PR for there site, other than money PR has no benefit.
I haven't promoted my blog at all and for some reason I am getting people coming. I think Google gives some preference to its Blogger members. Cheers, Sparky