Is it necessary to submit your site for max. number of open directories.will it increase pagerank or not?How much time we have to wait to see rspons
I think google loves your sites linking with high PR sites whether they are directories of others..So its easy to submit to high PR open directories rather then requesting other high PR sites for backlinks or paid ads on these sites.. yes this too can affect your pagerank.. Just do your work of submitting to directories and rest depends on them when they are going to live your link..
Submit to directories indexed in Google. Many of the directories are not indexed, submitting your site there is pretty much useless.
Quality links does matter - if you submit your link on some gambing site with PR5 and your site's niche is about education or something else then I don't think it will give good PR juice to your site .. Relevent links are good enought though .. And one thing more , if there are already a lot of links on the page and you submit your link on the same page then it doesn't work aswell !!