[Max Pemberton] “1. What is the best way to import videos from my camcorder to my iMac?”
Moving files from external media, be it hard drive or media cards is simply copy/paste to your hard drive.
[Max Pemberton] “2. What are the best ways to export those videos from Premiere CS4 with the highest quality possible?”
In the Export Settings window choose H264 as the Format and one of the 3 YouTube Presets. This is about as good quality within Youtube limits.
[Max Pemberton] “3. How long does encoding usually take and what is the best way to do it?”
AVCHD can take forever to downconvert to SD without at least 2 4 Core CPUs. H264 is about as good as it gets.