The tip is to just do a Google Image search and use whatever images you want to use. Or to use their advanced image search and click the commercial use button.
I also see many "auto-blogging" software platforms that scrape Google images for automatic insertion of images to your blog.
Well, just so you know, DON'T DO IT!! Most of these images are protected under copyright and you do NOT have the legal right to use them. It doesn't matter if you click a search filter or not, it depends on where the images are and who they actually belong to. And they don't belong to Google.
Here is the latest article showing the amount of lawsuits filed from a recent photo floating around the internet.
New round of Righthaven suits over 'TSA pat-down' photo prompts surprise - Tuesday, Feb. 8, 2011 | 2 p.m. - Las Vegas Sun
Several quotes mention that the blog owners just did a quick search on Google Images and used the photo. Saying they do it all the time and have never had a problem.
Well, they are now being sued for $150,000.
So next time you need another image for your site, consider paying the $1 - $5 for a licensed copy instead of just scraping the web. If you use an 'auto-blogger' software that scrapes content and images for you, you may want to reconsider the settings.