...that actually degrade your PR instead of even being neutral , such as some Directories, submission services ?

Not really. Directories that promote themselves as "search engine friendly" can be safely ignored as a waste of money. That phrase is a tip off that they're in the business of selling Toolbar PageRank
because their entire site is focused on web publishers, not on attracting site visitors. Thus, their focus will be on artificially increasing their Toolbar PageRank in order to make the directory marketable. Usually, sites like those are simply ignored. Which is why I answered "not really" to your question as to whether it will degrade your PageRank.

Stop thinking in terms of PageRank and think in terms of traffic. When thinking of link building consider who your visitor is and what sites they typically visit. This leads to discovering opportunities for obtaining citations.

For the very basics of PageRank and links, review the original Google paper, The Anatomy of a Large-Scale Hypertextual Web Search Engine [infolab.stanford.edu]. Then move on to our link building forum [webmasterworld.com].

Good luck,

mb

Yes your site has very low back links you submit increase your back links through link exchange, bookmarking sites, article posting on relevant sites and blogs commenting.

I would completely disagree with this last analysis. If I had 10 links from sites like the BBC, newspapers and other authoritative sites I would be far happier than having 100 from less important sites. But, hey, that's just me :)

Yes your site has very low back links you submit increase your back links through link exchange, bookmarking sites, article posting on relevant sites and blogs commenting.

IMO, all bad ideas. These are inevitably going to be low quality links... and they won't help you. If you're lucky, they may be completely discounted and at least they won't hurt.

Unique articles might be of help if they're not simply hacked out reworked material. Stay away from article syndication directories or low quality sites. Frankly, I'd save the best material for my own site.

Google values "freely given editorial links" from high quality, relevant pages. Attracting these will generally require very high quality content on your own site. One of my tests is that it should be good enough that I'd want to bookmark it for myself.

Link quality matters much more than quantity.

Agree with Robert... Always go for quantity over quality.