I want to add some thing what others said:
Basically, the best way to understand early reflections are to hear them.
Record the driest possible signal, like record some words with speaking closely to your microphone. Then use a plugin where you can switch early reflections on and reverb off. I would use Waves TrueVerb for that.
When you are what the effect does, you can hear much easier how proffessional mixes, videos use reverb and early reflections. And by that, you can develop an instict for using the right reverb settings.
One other note: it's totally normal to overuse reverb/early reflections, as we always want to hear very clearly that we had added something. But this is wrong. Using too much of them masks the direct signal and it is very tiresome to listen to music, as your brain has to constantly decode the signal from the mud.
Not using any reverb, on the other hand, would sound like you put cotton balls in to your ears.