What is the best way to test VO2 & Lactate?

This maybe an old topic that I missed but I am going to ask anyway. How do I "accurately" test VO2 and my lactate threshold? Up until this point I have been kind of winging it as far as training zones go. The only test I have done is the max HR test that came with my Timex Bodylink. I think to take my training to the next level I need to pay more attention to detail. I think the first step in getting where I want to go is to find out where I am at. What is the best way to do this? Is it something I can do myself or should have test done by a professional? In every Ironman training plan I read training zones seem to be  the focal point. I know this is probably a total newbie questions but any advice will help. I already know I need to get back keeping logs. I have been training just not logging. Thanks!