Unless you are flying in or out of Bangkok / Phnom Penh, due to Cambodia's primitive infrastructure getting to Siem Reap can be a nightmare.
If you are determined to travel overland, it's worth checking out the website below. The author is clearly an old Cambodia hand and his site is filled with regularly updated info, tricks and tips on how to get around.
www.talesofasia.com/cambodia-siemreap-guide-get.htm
And loads of other nice stuff on the rest of the site.
Updates
Don't forget, if you're going from Phnom Penh to Siem Reap (or vice versa) the ferry is quick, scenic and you'll get good photos - way better than the bus though pricier. Caution during the dry season - sitting on the roof comes with a caution. Wear sunblock, but the boat, nicknamed Rambo, has been known to hit exposed mudbanks at high speed, sending rooftoppers flying.
Send your feedback or queries to been.there@guardian.co.uk
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