What's your strategy for guest blogging?

[10JQKAs]

How long?

a.) 500 words

b.) 1000 words

c.) As many as I need to get a link

How good should it be?

a.) Digg/StumbleUpon worthy

b.) A decent article that the webmaster wouldn't mind posting.

c.) Good enough for a link

Who should you go for?

a.) Go big or go home! High authority

b.) Start small

Other thoughts and strategies?

[Nick_Ker]

How long?

As long as it needs to be to be good: informative, entertaining, thought-provoking, or in some way useful.
That said, the "SEO by numbers" crowd would tell you more than about 450, but less than 1000 words.

How good?

Shouldn't it always be your best? Sure, occasional fluff and filler is ok on your own blog once in a while, but when guest blogging, you should always make a good impression.
Think about guest blogging (and just about all links, really) as being a possible first point of contact with new customers/readers/whatever, and not just what it means for your rankings.  I think "content marketing" is the buzzword that people who use buzzwords are using about guest blogging these days.

Write the kind of articles that people will read and think "I want to see more of that" and actually follow your links.

Who should you go for?

Aim for the top authorities in your niche. But before contacting the site, really look at the quality of your writing and make sure it is up to their standards. Sure you could aim lower and be more likely to get your articles posted, but you would put forth almost the same effort without gaining as much from it.  Again it is an opportunity for publicity, in addition to an opportunity to get good links.

[Sebes]

I would also consider whether you are only in for a link or if you are in for reputation. If all you are interested in is a link i would just do enough to get the link, 500 words and good enough.

If you think the blog-owner or his audience is a valuable multiplier, then I would go for the best I can do. Opens the chance for more guest blogs on the same or other related blogs, improves your reputation and after a realy good guestblog you might also get free coverage following. Build a relationship with your niches authorities, help them and they will help you.

[DanielFreedman]

Why is this even a discussion? It should go without saying that you always want to put your best face forward.

Why risk your reputation with a "good enough" post that gets you the link but could engender a neutral or negative reaction?

The way I was brought up, when someone was nice enough to invite you into their house...you were on your best behaviour.

[10JQKAs]

Well there's miles difference between good and great. I'd say a good 90-95% of blog posts out there (let alone guest blog posts) aren't StumbleUpon worthy - and most fall within the "good enough" range.