NS2 has some significant gameplay differences from NS1, some of which are not obvious by simply jumping in and playing (such as the split between personal and team resources). Here's a few links I've found useful:
Community Wiki. 15 minutes spent reading up on structures and lifeforms will go a long ways towards educating you on what's changed since NS1, and how you should approach playing NS2. Take what you read on the "What's new from NS1" page with a healthy helping of salt, as there is quite a bit of inaccurate information there.
Marine Commander Tutorial. It briefly explains the difference between the carbon (green color, team resource) and plasma (blue color, personal resource) resources at 3:00.