How Do You Write reviews for software or plugins?

Hey guys,

I've been contacted by the company who made Squirrly SEO to write a review for their plugin for wordpress on my blog about blogging

But to be honest, I have never done this before. Is there anything I should look out for? Is there some tips for how to provide good value for my (few) readers and also for the company?

They want to offer me 1 year worth of subscription to their plugin and that sounds awesome. So I want to really help them out, because the plugin is good.

Check out other reviews, you can check CNET and PCMag for ideas. Do add a con or two to the pros so it doesn't look like you are fawning over them.