Before I buy any new makeup, skincare, fragrance, haircare, or anything at all related to beauty, I go on Makeup Alley. It is the holy grail of makeup review sites. What it is is that people (normal people, people who work in the beauty industry, beauty bloggers) write reviews of every beauty related product imaginable. They rate them on a scale of 1 t0 5, talk about their experience with the product, usage tips, post product swatches, etc. Some products have over a thousand reviews.
It's really helpful to find new uses for old stuff (look up honey) and to see if a product is going to be right for you. For instance, if I'm debating between two eyeliners, I'll look them up on Makeup Alley and see what kinds of reviews they got. Go check it out today!