Screenshots are not part of the UI on Moto phones at this time (I hold out hope it will be one day )...however, there are a couple of apps in the market that do not require you to root in order to capture screenshots... the only one that I have experience with is "no root screenshot it" by Edward Kim - it is a paid app but it works very well...Screen Capture - No Rooting 2.2, aScreenshot, Screenshot UX are other possibilities...
If you do decide to root, then there are a few additional options - Screenshot ER is one of them and is the one I currently use.