Is the page linking to you indexed in Google and is the cache version fresh?
Why is this essential? Google has a cached page of any indexed page on their index. So basically, this should be your starting point for any link partnership decision. You need to verify that the page the link partner is proposing for exchange, is actually indexed and that the cached version is of the page is fresh in their records, within 20 days old as a benchmark. This will show that the page in question gets crawled often. PageRank of the page issecondary, and comes normally afterwards in comparison to this primary check.
Is the page linking to you on topic? Is this a themed link?
There is a big difference between the types of links youcan get. These type of link are very targeted and carry a lotmore weight over generic or unrelated links. This is part of what explains why some sites with much less links that their direct competitors are able to outrank them for particular terms. Quality links from themed sources is the short answer. Focusing on just "popularity" and inadvertently ignoring "reputation" is a mistake a lot of online marketers make. Keep this in mind.
Is the Title tag of the page linking to you on-topic? What about the text?
The title tag of the page linking to you is of great importance. When that is combined with text that is on topic with the page which is being link from, and otherfactors, the link value is increased greatly for the link. So as you can understand from this, is all about the co-relation of these factors that makes one link better than another.
Where is your link on the page located? Navigation, gutter, footer, body?
How many other links are on the page? Home Page vs. Link Page PR gap?
PageRank gets automatically diluted in relation to the amount of links on the page.
Google guidelines currently suggest a maximum of 100 links per page. So here you