Giving feedback on a product or service may seem easy enough. However, if handled poorly, you can come off all wrong and send the wrong message.
First, be candid and frank with getting personal. If you liked the product, state what it is that you liked. If something about the service leaves you cold, write out what it is you think is missing (plumber stood too close to the door upon arrival and invaded personal space...mowing company came and left without any notification).
Second, be ready to sign your name or screen-name. Take responsibility for your comments and give the company the abiltiy to get in touch with you if they have further questions or need clarification. I know this may make a person feel uncomfortable, but at least you know they heard you and are making attempts to improve.
Third, keep a helpful tone; don't be mean spirited. A well thought-out comment will be readily received whereas a review written using harsh language and vague examples will be passed over and dismissed. To emphasize this point, let the company know you are sending the critique to help them improve. Your choice of words are crucial to getting your point across and having the recipient "hear" what you're trying to say.
Good feedback helps everyone and can help improve or reinforce the quality of products and services we buy in the future.