Link Mechanics

Here's a quick summary of  the link quality portion of an internal seminar that we had on SEO. 
1.  If I put two links from one page to another page, does the second link help at all?  NO. NOT AT ALL! The second anchor text and link are totally ignored.
2.  Are links from images or links from text more valuable from a SEO perspective?  Text links are preferable.
3.  Are text links within the body content more valuable then links elsewhere on the page?  Links from within the body of a paragraph are considered more likely to be organic references and hence, count more.
4.  How many links per paragraph is considered too many?  A very rough rule of thumb is that one link per hundred words is optimal.
5.  Is a sidebar link superior to a content link?  This is really a repeat of question 3 above.  In content links are considered the best.
6. Is it better to use a shotgun or a rifle?  Of course, what I mean, is it better to target a page by using the exact same anchor text over and over again or to vary it slightly?   Slight variations are more natural. So if you are targetting "delicious hot dogs", you might try variations such as "hot dogs","hot delicious dogs","tasty hot dogs","delicious dogs","delicious  sausages","yummy frankfurthers". The idea is for it to be natural, not highly organized.  I'm betting that Google will start figuring out synonyms soon (ie latent semantics in the jargon of search).
7.  Are run of site links valuable? It's hard to tell, they certainly aren't very valuable. On one hand, Google might consider them to be bought and worthless like so many footers. Or, like so many blogs, they might be considered truly natural endorsements. 
8.  How important is the relevance of one site to another, of one page to another, in terms of the value of the link.  VERY Valuable.  If you are on a site called homeschool freaks and you link to another page using homeschool freaks as the anchor text and that page is titled homeschool freaks,Google takes that endorsement very seriously.
9.  How much more important is a good site from a great site, a PR of 6 over a PR of 3?  This is a great mystery but I would guess that each PR (all else being equal) is one order of magnitude more important than the previous level.  So, ten links from sites with NO page rank equal the value of a PR of 1.  A link from a PR of 5 is ten times more valuable than a link from a PR of 4.  Note that I say; "all else being equal" which means relevance, number of outgoing links etc. Also note that I have not seen anybody else even attempt to quantify this which means that they are all wimps.
10.  Does a site's organization matter in terms of link quality? Yes, Google likes content sites organized into content areas that it understands.  This is a confusing and ambiguous area. Is Google looking at internal link structure or to folders? One one hand, I hear that they discount pages that are far from the root directory by every folder so I try to keep everything close to the root. On the other hand, this simplistic rule makes no sense to me so I don't want to take it too seriously.
11. How can you tell how credible a site is to Google? Easy, search a bunch of relevant terms and see how high in the search engines it is?
12. Is there a simpler way to see how credible a site is? Maybe, try using a link counter and then evaluate the quality and relevance of the links. Also, check out how old it is. And see if the links come from .govs or .edus which probably count more. There are tools for this.
13.  Do title tags on text links and alt tags on image links help?  What about adding a title tag on an image link? All the tags help, the title tag on the image is a little extreme but maybe worthwhile.
14.  What's the best links to focus on?  This is really a rehash of much of the above especially the rifle vs shotgun and run of site vs natural questions.  The best thing is to have a natural looking mix of links which grow steadily.  Growing by 10% in a day or a week is, for established sites, an upward limit. More is weird an merits being looked at.  Just keep tryign to get more links of many different types on an ongoing basis focusing on mixing it up and mixing it up.  This is the natural pattern of the messy world and shows that the links are natural. LOL!

Tools
majesticseo
yahoo website explorer
Google's wonder wheel
seomoz.org
raven-seo-tools.com

Terms

Trust
edgerank
title tag
alt tag
halo link