There are some basic things you can do to improve the overall audio quality of your YouTube videos. Some of them require using special equipment, others require software or techniques. Use a Dedicated Microphone Using the onboard audio of your camera is generally bad idea. Usually the microphone is too sensitive and pics up everything including background noise and wind. There are also times when the auto settings on the audio input levels make the sound inconsistent. To avoid this use a dedicated microphone like a lapel mic. If you're camera has an audio input jack, use a lapel mic directly into it and you will get better quality audio that is easy to work with in editing. An alternative if you don't have an input jack on your camera is to use a microphone and digital recorder, and clap at the beginning of your videos so they are easy to sync in post. If you can't afford a digital recorder you can use your smartphone in most cases. Screen Casting If you are screen casting, one of the best things you can do is buy a USB Dynamic Microphone. These microphones are unidirectional, so they only pick up sound from one direction. These are usually in expensive and produce great quality sound. I cover more tips like this in my video below, including software you can use to improve the sound quality of your videos, and links to where you can buy the hardware I discussed.