- Is the site relevant to your site.
Many will argue relevance isn't important but I say to hell with them, a lack of relevance is a spammy approach, don't do it.
- Does the site link out?
There's no point sending a request for a link or guest post if the site clearly doesn't link out.
- Is the site indexed?
If the search engines don't know about the site why bother unless it's a new site and you expect it to get indexed.
- Do they invite submissions and suggestions?
If the site actively asks for suggestions for content or links all well and good but some sites actually advise they don't, why not check?
- Is the site established?
An established site is always a good thing when it comes to link building, but don't rule out fledgling sites, they might be the next BIG THING.
- Can you find the people behind the site?
If it's an automated blog (splog) it might not be worth the effort of making contact.
- Is the content current?
Establish if the site is a living breathing thing that's still being developed. It's amazing how many false positives link building tools throw up to sites long since defunct but still live.
- Is the content any good?
This is a hard one. What I think's good you might think's rubbish but be sensible and objective and you could save yourself some effort.
- Do they invite and police comments?
If they do it's a good bet the site's active with real people behind it.
- Do they provide editorial links?
Look at the type of links they have, if they only have "here are some of our friends" type links maybe don't bother.
Link building is hard enough without wasting your time going after links you'll never get. Hopefully this check list will stop that from happening.