If I may join in, as a professional reviewer of 19 years, albeit more for PC hardware than audio, there are a few things one has to get to grips with before one starts:
1. You can't please everybody, so don't bother pleasing anybody but your own conscience;
2. If you please your conscience, you won't make serious money out of reviewing, but you sure will get a lot of people VERY mad;
3. Before you start, leave all your biases at your home, in your own system - that is the ultimate statement you can make, although if you remember the point under 2., it will probably not reflect your tastes too well simply because you won't be able to afford it;
4. If you are a reviewer with a system costing $100K+, you are on the take, period, unless you were filthy rich before you started out;
5. Before you say anything about anything, make sure you have walked it through at least three systems in three rooms, every time for at least a week (yeah, I know I'm nuts, NOBODY has that much time, it seems, but my poor self - but then, I don't have the biggest, baddest system every month a new issue appears, and I can afford a new car only once in 9 years);
6. If you want to be honest, you need to keep a lot of stuff handy, including some costly items - no matter whether you are testing a $200 integrated or a $200K pre/dual monoblock configuration. If it's good, you'll hear the difference with improving ancilliaries, but if you don't, or if the difference is small, you can take out the manufacturer no matter what his name is and how much he's worth;
7. You need to keep a very solid collection of high quality recordings if you are to give it a fair chance at showing what it can do;
8. You need to be able to call in others and have them tell you what they hear without knowing what you think, then you need to cross reference that against your own findings, possibly redo something, and
9. You need a fair knowledge of practical electronics to be able to diagnose some things. For example, if somebody tells me he can squeeze say 400 watts in impulses from his amp, and I see two pairs of say 130W output devices on a small heat sink, then I know he's scamming me. That power may be available, but it will be there for a meaninglessly short period of time, else the thing will overheat and burn out, etc.
I lost the tenth point somewhere on Mount Sinai.

One more thing - getting there is not too hard. It starts being hard when you realize people believe you; then you start worrying whether you were quite right, because if you boo-booed, somebody ends up shortchanged when he shouldn't be. This slowly turns into a nightmare over years.
Cheers,
DVV