If you arrive in Siem Reap within the late afternoon, do go and buy your pass at 5:00pm. They'll let you to the compound and you could find a sunset (the sunset pictures are wonderful at Angkor Wat westside). Your pass can be activated the following day.
Do specify what type of Angkor Wat pass you need. The regular passes are great for one day ($20), 2 or 3 days ($40) and one week ($60), but you could have the 3-day pass to use within 1 week, and also the 1-week pass for use within 1 month. Make sure you specify this during the time of purchase.
Do keep the pass handy, while you will be asked to show it whenever going into the temples. A plastic pass case on the leash comes in handy, and can protect the pass from getting dirty or damaged.
Do hire a guide if you wish to have in-depth historical and social information as well as get access to the most impressive paths where to understand more about every temple. The guides also realize exactly where all of the great carvings/reliefs are and will explain to you those as well. The guide can also be responsible for organizing transportation, so do specify if you want to travel by tuk-tuk, car or mini-van.
Clothing
Do wear light-weight clothes. Whilst numerous people choose ethereal cotton fabrics, other people choose synthetics for example the kind that you can get at mountaineering shops. The climate is really humid more often than not, and also the synthetic fibers wick away perspires and dry on the body.
Don't wear unveiling clothing- short pants or midriff-baring tops, low cut blouses, etc (specifically for women). Longer shorts, like right above the knee or Capri jeans are perfectly acceptable. Do remember that if you need to climb up to the towers atop Angkor Wat that both women and men must be "respectfully dressed", for example covered shoulders and chest, and long pants or skirts (long shorts are acceptable).
Do bring a hat or cap, and sunglasses.
Do wear sensible shoes. Whilst formally the temples can be done in a set of flip-flops, it might be a wiser option to use a set of hiking sandals for instance Teva or Keens. (Toe coverage is another good option.) While sneakers and socks or hiking boots might be overkill with the heat and moisture of Cambodia , the bottom line is to wear what you feel comfortable.
Don't forget a light jacket (such as micro fleece) for earlier mornings, particularly if you are getting out by tuk-tuk or motodup. It will get very freezing within the wee hours with the wind blowing, particularly in the chiller months.
Money and tipping
Do take small bills (US$1 and $5) for shopping and tipping. US dollar becomes unofficial currency in Siem Reap and the majority of vendors, even street vendors prefer US dollar. Vendors merely price their products in US dollar but many market vendors will not have change for any $50 bill.
Don't change US dollar into the riel in a bank and you may lose about 9 percent since bank exchange rate is at 1 USD= 3700 riels while vendors are pricing at 4000 riels. In case you receive large bills from bank such as 10000 or 50000 riels, it'll actually make harder for tipping. Riels in small face value is nice to have and handy for tipping, as well as for donations when going to the temples.
Do tip for outstanding service. This consists of guides and drivers (roughly $2~$3 per day, each), masseuses, and waitstaff at restaurants. For waitstaff, "rounding off the bill" by leaving some bills (riel) would be fine. Do know that tipping isn't expected, but can be really much appreciated, and whether or not to tip the amount to be offered is totally up to the discretion of the visitor.
Do critically think about exactly what you will be doing before buying products from kids in the temple. If they're making money there, why should they bother to go to school? In addition, the books they are selling are cheap copies and also the authors don't get royalties from the sales. Sharing a smile or a chat with these children is really a better option, and at least they'll reach practice their English with the friendly visitor.
Safety and health
Do sign up for an insurance plan which will include treatment or incidents before leaving, or consult your insurance company at home to know whether you will be covered when abroad.
Do use sunscreen. You could take your favorite brand from home, or buy it when there.
Do use insect repellent. As the risk of contracting malaria is very low in the immediate Siem Reap area, if you are going to the countryside (Phnom Kulen, Koh Ker, etc) then you'll need to use a good DEET-based insect repellent. Repellent having a concentration of 25% is enough, and will be used every 6 hours or more often whenever you sweat. Keep in mind, the sunscreen goes on first, the bug spray last.
Don't forget to drink lots of water. If you're not used to humidity (or dry weather), you could easily get dehydrated. You should check with the driver in advance to see if he supplies water (many do, as well as have a little cooler). Otherwise, bring one bottle on hand and you may buy more on the way.
