I'd treat directories with caution - not sure that they make a huge difference to your PR in many cases
I don't bother with directories, takes a long time to submit to them and they really make no difference to the sites i used them on. Buying backlinks has worked ten times better.
i like blog commenting and forum posting since it's free. don't spam, make sure you contribute something that is on topic. and not just "good job dude".
How do you buy backlink? I am sick of doing link building, and keen to know how to effectively buy backlink. Please reply this message. Thank you very much!