What are the best quality backlinks?

All of them matters.

Get as many as one way inbound links.

for me Directories and Forums are my top choices...

FFA's or linkfarms are SEO's worst nightmare

how about directory submission?

i suggest related site(Content) is good link for SERP

try also link trades....

You can create quality backlinks (one-way) every day by posting comments on blogs that
have content close in theme to your most important keywords.

Use Google Blog Search at:

http://blogsearch.google.com/

Each day type in one of your most important keywords. You will be presented with current
blog posts relevant to the keyword.

You will be able to leave a link to your Web site/blog in the comment process.

You may enter your keyword in the name box, and it will show up as a hyperlink.
In the url box goes your Web site link.

Most bloggers will not object if your keyword entered in the name slot is closely related in
theme to the nature of your comment.

Do not spam, that is make frivilous comments just for the sake of the link.
Only make comments when you can add something useful to the blog post.

Try to make 3 comments every day, and over the long term you will build a strong
backlink structure.

Robert

You may also try deep linking and link bait for your site

The best way to attract quality relevant inbound links is to write something that people will find useful. Write killer content that people want to link to, optimize the content and the page it is on to the best of your ability and put it on your Web site, and let people in authoritative positions know that your page exists.