General Layout
The whole region with the temples, monuments and walled complexes is officially called the "Angkor Archeological Park," and is commonly known as just "Angkor." Angkor WAT is just one of the sites, albeit the largest and most well-known ("wat" is Thai for temple). So it’s more accurate to say that you are visiting "Angkor", not "Angkor Wat", since Angkor Wat is only one of the hundreds of sites within Angkor.
The archeological park covers nearly 80 square miles and contains hundreds of monuments – there are vast walled compounds, an ancient walled city complex, and countless temples and monuments. The complexes are separated by dense jungle and are within a few minutes’ vehicle ride from one another.
The nearest city is Siam Riap, 4 miles away from the entrance to the sites. The city itself is quite small, so a central location for your hotel can make your stay more enjoyable - hotels on the outskirts of town may literally have nothing around them.
Passes to the monuments
You should only purchase your pass at the official entrance to the site (there are rumours of scams to resell used passes - whether it's your hotel or guide or someone on the street, don't be tempted - you need to buy your pass in person at the entrance to the complex). Bring passport-type photos with you; they will take photos for you if you don’t bring them, but you will have to wait. The passes are $20 US for one day, $40 US for 3 days, and $60 US for 4 – 7 days.
Guide vs. on your own
Guides are readily available at the sites themselves and in Siam Riap for several US dollars per day.
In general, I prefer to have a guide for at least part of the time when I travel. In Angkor, we elected to visit the sites on our own with just a guidebook and enjoyed the privacy and freedom to explore on our own, but a guide would have been extremely interesting for at least one morning or afternoon. Part of what makes Angkor so amazing is that there are very few other tourists - if you're lucky, you may find that you and your companions are frequently the only people at a given complex. The temple complexes are amazingly vast, and you can explore all the rooms, courtyards, and terraces in solitude without seeing any reminders of the outside world. We found that doing this on our own and reading up on the details was far more enjoyable than having a guide alongside us.
If you choose to hire a guide for most of your trip, do plan for at least one morning or afternoon on your own (at one of the lesser known temples you'll have a better chance of being alone) - it's an incredible experience.
The guidebook we used is readily available for purchase in the city of Siam Riap, at the entrance to the sites, and in front of the major temples. We used "Ankor" by Dawn Rooney (published by Odyssey Guides), which, despite the numerous site maps, we found very difficult to follow on-site. It makes a good armchair guidebook, but is unreliable for navigating the sites. Some of the directions are clear, but more frequently, the book describes an interesting carving or architectural detail while providing instructions for locating it that are so vague as to be completely useless. I haven’t had the chance to compare it against other guide books, but I’d recommend trying to find another if possible.
For at-home reading, I HIGHLY recommend "Angkor: Cities and Temples" by Claude Jacques and Michael Freeman. Copies are available in the city and airport of Siam Riap, and also in Bangkok, but the historical explanations would be wonderful to read in advance (the price is roughly the same on Amazon.com - $56 US - as it was to buy in Cambodia).
What to bring
Clothing: The standard recommendations are for men not to go shirtless and for women not to wear clothes that are "too revealing." We saw all ranges of clothing, including many people who weren’t following the above guideline.
Footwear: Being generally opposed to trainers in public unless one is actually training, I brought both "sturdy" sandals and Keds-type trainers, and ended up (grudgingly) wearing the trainers most days. There is a lot of climbing and clambering around that can be done, and endless unbelievably steep stairs to climb, with loose stones throughout. You will not regret having sturdy shoes, but you may well regret wearing flimsy sandles.
Other: Absolutely don’t forget sunscreen and mosquito repellant! Also, you may want to bring a couple of books that would help children with their English to give to your guide(s). Most of the people here speak very, very good English, but our guide told us that English books can be hard to find and would be appreciated by almost everyone. Even if your guide speaks perfect English, he will surely know someone who will appreciate the book.
Food and miscellaneous
Those who like Thai food will be in culinary heaven in Siam Riap. All of the hotels have restaurants, and there are several streets in town lined with many dining options, not including the countless outdoor local food stalls. Almost all restaurants (even the local food stalls) have menus in English, and the wait staff all speak enough English for dining purposes. For those who are less adventurous, there are plenty of more familiar choices, including pizza and even Mexican food!
There are dozens of little stalls at most of the sites selling film (along with water, cola, beer, snacks, postcards, and souvenirs). We had our film from the first day developed at a one hour Kodak store in the city while we ate dinner, and the pictures were developed very well.
Accommodations
Almost all hotels and guesthouses claim to be just a few minutes from the temples, a few minutes from the airport, or a few minutes from the center of town. Siam Riap is a really small town, though - ALL hotels are a few minutes from the temples and airport, and being 5 minutes from the center of town means that you might find yourself OUT of the town.
Be sure to get a good map of the hotel’s location and check it for yourself. In my opinion, being closer to the center of the city is more important than being closer to the temples, unless you are on a bicycle. The temples will be a 10 - 15 minute ride from your hotel (by taxi or motorcycle), so an additional 3 minutes is not too important for the trip. If your hotel is on the outskirts of town, however, (like the Sofitel, the hotels on the airport road, and some guesthouses), you will find that you need to take a tuk-tuk or wald for 10 minutes to find restaurants and shops.
There seem to be 4 major categories of accommodations Angkor:
5 star luxury hotels: Includes the world-renowned Grand Hotel d’Angkor, built in the 1930’s in the colonial style (starting around $250 US/night), and the brand new Sofitel (starting around $130 US/night). These are on the edge of town closest to the temples. Don’t be fooled by the Sofitel’s claim that it’s "the closest hotel to the temples" – it’s only 4 minutes closer to the hotels than the Grand Hotel is, which only means that it’s farther from town.
Mid-range hotels from $80 - $100 per night: Many of these are located on the outskirts of Siam Riap on the way to the airport (not on the side of the temples). There are a few worth investigating in the center of town, including Angkor Village, which looks charming.
Budget hotels for around $30 - $50 US per night in the center of town: This is the type we stayed at – I'd categorize them as barely passable – no "highlights" other than price. Clean, nondescript, serviceable rooms with private bathrooms and air conditioning, right in the center of town for easy walking to restaurants and city life.
Guesthouses catering to backpackers for under $10 US per night: These can be really "roughing it", and it’s a case of choosing your priorities carefully. Not all are centrally located or have private baths and/or air conditioning, but you can find some that have all of the above, so check around.