What effect does submitting articles have on your sites rankings?
Can it really boost your ranking in the SE's?

Not rankings so to say. well it could as you can get backlinks if people use your article on their sites.
But, main thing is that you get good traffic from people clicking the link in your signature at the end of the article,

It can help your rankings too though, by giving you links which is how google ranks your site pretty much.
There really are no negatives to submitting articles.

Submitting articles is the easiest and best way to promote your site! Its free and quick and lets so many people see your website.
I cant understand people who DONT do it.

great, I will have to do more of this then!
Just to decide whether to write articles myself or pay someone now..

Wouldn't one of the negatives be if the article site is PR1 and your site is PR5? Is that a negative or not? I usually try to link to sites with an equal or higher PR myself.

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Green Diva

Only articles cannnot helps a lot in increasing Page ranks so i suggest you to follow all seo techniques to have high page ranks

I have some ebooks I wrote on crafting and am publishing at lulu. I am a bit confused about posting articles. Are there any ruels or places.. what do you usually put in an artcile?

No, that is a definite positive for you if you're the PR5, and it won't hurt you to link to relevant sites of lower PR. You just want to avoid link spamming.