In Europe, I always check the price directly from the hotel, if it's last minute, I check hotels tonight and if the price is really much cheaper in booking.com, I call the hotel and get them to match the price.

I sometimes use hotels.com though since I often can get a 5% cashback plus their reward scheme which gives me a free night every ten nights (effectively a 10% discount)

Oh and for reviews, I check tripadvisor since, on the contrary to booking.com, they actually publish bad reviews.