How quickly after starting a blog should I put ads on it?

Darren at Problogger has a great post on running ads on your blog - should you run them from day 1 or wait until you have significant traffic?

Advantages to putting them in immediately include that you get experience with ads and can work on optimizing them. Also, readers will expect ads and not get angry when you add them later (and some quite well may).

Disadvantages? "This argument is basically that if you put ads on your blog from day 1 that you potentially turn people off your blog because it will look too commercial or too much of a money grab."

Of course you may not to run ads at all - ads do take up valuable screen real estate that could be used for something else.

For example, I have a picture of my book and an invitation to subscribe to my newsletter BizBlog+ in two of the prime spots for ads. I think I'm better served by them than a few dollars in ad revenue - but I may change my mind some day! (although in reality they are ads of a sort themselves)

You may also not want ads as you may think they'll detract from your professionalism -- could you imagine AdSense on GM's Fastlane blog for example?

In the end it's a personal decision - there rarely is one correct answer: ads now, ads later, ads never.