I would highly Mr Khemara as your tuk tuk driver cum tour guide for any first time visitor to Siem Reap. Mr Khemara is very knowledgeable, friendly and punctual. He is always half an hour early waiting for us at our hotel. He took good care of my mum during the trip. My mum always joke that he is her walking stick.
I am also impressed with his wifi tuk tuk. He also help us to take a lot of photos and tell us where are the good spots for taking photos.