The best source of information is your EARS. Form your own opinions, don’t just accept what other people say. Believe what your ears tell you when listen to music!
Remember that many people who write about audio are biased in one way or another. Beyond that, There is often a lot of hype to justify very expensive equipment and the perpetual upgrade switch around game. You might want to use some of the information from the community to help you narrow down what you would like to take a first listen, but you need to listen for yourself.
Purchase what sounds good to you. There is no reason to spend $15,000 on a high end system if you don’t notice significant difference between it and a $2000 system, or for some people, a $200 system.
I would suggest doing blind A-B testing whenever possible. Blind A-B is were you do back-to-back comparisons of two (or more) pieces of equipment, but have no knowledge which is which. When doing blind testing it is important to vary only one thing. For example, when you switch amplifiers, you need to make sure the output levels are equivalent. This is possible if someone is willing to switch equipment around, not telling you what they are doing, while keeping a record of the sequence used. This said, 30 minutes of blind AB testing in a showroom is not a sufficient. You really need numerous hours to fully evaluate a piece of equipment. Also remember that you get used to a particular sound signature so you need to have enough time to get use to something that sounding different.
I have found that knowing what equipment I was listening always tainted my evaluation of the equipment. In particular, I tended to favor well regarded equipment (e.g. more expensive) even when I couldn’t tell a difference in blind testing. There is a nice write up about blind vs sighted testing and the bias when people know what they are listening to.
Make sure whatever you are comparing have been volume matched. Higher volume is almost always favored. There are very fancy way to attempt to volume match to components, but a good starter method is to play pink sound through the system while placing the microphone section the ear buds that likely shipped with your smartphone in front of the speaker or inside the the headphones. Use a sound level meter application to measure the volume of the pink noise. Adjust until volumes match.
When evaluating new equipment you should listen to music you know well. Ideally music that you have heard live. I have found that female vocalist, percussion, piano, violin, and cello solos are particularly helpful in evaluating equipment for good timbre. Choirs with a large orchestral backing can help you determine how the system renders very complex sounds. There are a number of audiophile recording companies like Chetsky have samplers which can be quite useful and companies like hdtracks which specialize in high fidelity records. Audicheck.net also has some useful audio tracks. I would suggest though, that the music you test with is primarily the music you listen to. I would also suggest have at least a couple of tracks which aren’t well recorded because you will likely have some music that you love but is poorly recorded. You will want a system that doesn’t render this music painful to listen to.
I encourage people to consider that what sounds good at first might not be a sound you want to live with. A powerful bass may seem rockin for a few minutes but but very well may sound boomy if you have to listen to it for hours. Better quality audio equipment is neutral, allowing each piece of music to sound as it was recorded without adding or subtracting anything.
While you need to form your own opinions, it can be helpful to learn from others, both to prioritize what equipment to listen to, and to discover equipment which you might not have known about. A technique that I have found to be useful is to read reviews about equipment I have listened to myself. My goal is to find reviewers whose opinions are well correlated against mine. When I find a reviewer that seems to have similar opinions, I prioritize the list of equipment I want to listen to based on their opinions. The reviewers have listened to a lot more equipment than me, so why not use their experience to prioritize my list. For example, if I have listened to a particular headphone I thought was really good, I will look for reviewers who agree with me. Then I will see what other components they liked. The components they liked (which are in my price range 🙂 would go to the top of my “try it” list.
BTW: Something that might be useful as you read reviews is know that is the audio community there are a variety of descriptive words that have specific meanigs to that community. There is a brief sound description glossary which was assembled at head-fi.