Blog reviews are much more efficient and effective for product/service promotion because influential bloggers have a huge user base and users trust the bloggers opinion for the most part. If such bloggers endorse a product/service, chances of users acting upon bloggers recommendation are more when compared to promoting through a flashy banner or a text based ad.

Anyway, getting back to the point. "To Do" List for Product/Service Companies before they Approach a Blogger for a review or promotion.

1) Write your own review and send it to the bloggers, let them read and understand your product or service even before they use it..
2) Send your product to the blogger.

• If its a paid software then do send a registered, fully functional software. It wont hurt
• if its a paid service ask the blogger for an ID for free registration with full access.
• If its a product, send it at the time of requesting a review

3) Mention a list of features and topics you want the blogger to cover in the review
4) Mention the target audience for a better (may be) more personalized writeup.
5) Do include a fact-list of the product
6) Offer free downloads,  exclusive beta invitations or something which gives a sense of differentiator to the blog readers

These are few things I could think of. Do leave comments if you see something missing on the list. Especially bloggers, if you see something missing, I’ll be happy to update the list.