If you're not in Angkor Wat, you'll probably be on Pub Street getting drunk off the .50 cent beers. If not that, you'll be at Happy Herbal eating yourself into a self-induced coma. Those are the only two things anybody does in Siem Reap; kind of like going to New Orleans for only Mardi Gras . Siem Reap should be a three day-max stop with all three days spent at Angkor Wat and nights on Pub Street. The rest you can avoid. Simple as that.
Insider Tip:Stay safe, work in groups, and don't get too messed up. Also wear comfortable shoes to Angkor Wat.