#6 - make sure you completely read and understand what your paying for.

Earlier this year, I was trying to plan a migration from Rackspace to AWS - brought a database server online at AWS on par with the size of ours at Rackspace and did some testing (to try to simulate a real world scenario). Got distracted by some other projects for a few weeks and all of a sudden comes a bill from AWS for almost a grand - we "didn't even use it"

Fortunately, as a 1 time courtesy, they credited it back, but the boss was definitely not happy, haha.

Be very careful what you turn on and what size it is.

Rackspace, is a bit more clear on pricing IMO.