What kinds of back links are considered the most powerful?

Three of the things you mentioned may not matter at all, and domain age is not 100% always a better link.

Build lots of links with anchor text.

Try to get links from article submission sites as well as web 2.0 properties - Squidoo, Hubpages, wetpaint(indexes fast), Wordpress, Blogger, and the list goes on and on...

You can get backlinks through blog commenting/posting, forum posting, posting to web 2.0 properties such as hubpages and squidoo, article submission as well as video submission.

Profile links work pretty well, especially on less competitive words. Writing articles and submitting to Ezine is really good.

You said what you were familiar with but you didn't say what you had actually done that didn't work.

profile backlinks is good.
i am no.3 for 100.000.000+ keyword search in google only use profile backlinking.

The anatomy of the perfect link:

1) Keywords in Anchor Text
2) Is on a page with few other outbound links
3) Is on a page with good PageRank
4) Is on a page within a domain with good Authority
5) Is nestled within the content of that page

Very difficult to get though.

The rumours about .edu and .gov are false. Matt Cutts has said that no extra weight is given to these domains. However, theyu do tend to have good authority due to their content and importance.

To created effective links, try these:

1) Forums
2) Blogs
3) Web2.0 profile sites
4) Press Release and Article Directories

These are pretty low level. The best backlinks are "natural", ie you haven't put them there. To get these you need great content and you need to let people know about it.

Case study:
Last year I worked on an architectural site and the company designed an eco-house. I drafted a press release and sent it to 5 of the major architecture blogs. It was featured on 4 of them and within a few days, we'd been featured in over 400 blogs around the world and gained a huge amount of natural, keyword rich links. The PR of the page they were linking too, an internal page about the eco house, shot from 0 to 4 and it hit the first page of Google for "eco house" within a couple of weeks.

The only way most people can obtain better links than the low value ones mentioned here is
to spend some time "powering them up".

Each back link is valuable and will help you to reach your goal, it's doesnot matter how old your domin it's matter only back link create back link as much possible using your keywords

Well other than do follow, relevant theme, domain age and pr you need consider anchor text that must have your main keywords and IPs, you try to get links form different IPs as many links from same IP consider as no more than a single link.

From my experience Dofollow blog commenting is a powerful way to create backlinks. If we get backlinks from High PR pages, niches related, new blog post etc we are in the game.

Thanks
Blog.

Best Link: High PR related content with anchor text to your website
Good: Low PR - Title Tag has Anchor Text - Content is Related - Using your anchor text.

There are 3 for backlink.

1. Much

2. Relate

3. high pr

relevant link with authority might be best one

I know some people will disagree, but from my own limited experience I have seen competing fresh sites outrank older ones by only having a few, sitewide links from aged,high pr domains. Alas, shell out the dough for some real high pr links.

Make sure link to sites that are related to your website.. Like for example putting links in same niche websites :-) That will help so much!

A Warrior member conducted a study on backlinks, and part of the study covered relevant vs irrelevant sites used to backlink, and he found that it made no difference where the links came from. You can read about it here: 60 day backlink experiment.

I think first it goes with do follow links with article submission.links from web 2.0 sites and directories sites

The backlink can bring two benefits:
1. Higher page rank: the link on the linking page with high PR and anchor text
2. Visitors: above plus the page should be related to your landing page

From experience, i have seem a dramatic increase in serp after doing anchored backlinks from site profile of high PR.

If you can get links from same niche then its the most powerful one. And as said above it is best if you can get link from some authority website or some high traffic website.

This is a nice share. I follow every of your share. You have really affected so many with your timely and huge share