Transparency is very important to me. If I received a product for free or at a special discount, I will always state that in the very first line of the review. If I got it on sale, I’ll generally say so too if I remember the price I paid, and I’ll mention whether I think it’s worth full price in my summary comments.
I try very hard to combat bias, so I break my reviews down into four categories (design, fit, function and build quality) each with a score out of 5. This makes my reviews as quantitative as possible, and also helps you determine whether the drawbacks of a product matter for your purposes. Check out my review format for more details.