Prepare your wallet
Home to the awe inspiring Angkor Wat, Siem Reap is the definition of a tourist city. Tourism is why it exists. Ticket prices for the main attraction are high, but become cheaper the longer you stay. A one day pass is $37 while a 3-day is $62 and a week long pass will set you back $72 plus transportation for the day. Hotel lodging is a little higher than most other southeast Asia locations, but the variety and quality are good. Massages, however, are still very cheap!
Wats take time
Some people spend a day, but you could easily spend a week exploring all the wats. And in case you didn't know, there is so much more than Angkor. Actually, there were several wats that we enjoyed more than Angkor. While you will most likely do more than a couple in a day, there are days and days worth of sites if you wish.
Dress for success
It's easy to forget that these temples are more than touristy site, they are holy sites which require appropriate attire. For women, this mean covering shoulders and knees. Men have less to worry about, but also remember the heat and humidity of the region. If you travel during the rainy season like us (July) bring rain gear or at least prepared to be soaked.
With so many visitors from around the world, you can find a huge variety of restaurants in Siem Reap. In fact, you really have to search for some of the traditional Cambodian cuisines amongst all the Indian, American, Mexican & Italian restaurants. On the contrary, you won't have to search far for some amazing beer deals on Pub Street.
Tuk tuks and taxis are the primary means of getting around Siem Reap and the Wats of Angkor. We personally enjoy experiencing tuk tuks and getting to know the local drivers. If you find a good one, they'll often go out of their way to chauffeur you around for the entirety of your stay. They appreciate the guaranteed income and you can gain an new friend in the area. As always, tipping means a great deal to them so don't skimp on appreciating your guides and drivers.