Ok, first, you need a video editor to edit everything (for Windows, I recommend Windows Movie Maker), whether you want to make a music video or just point the camera at you while you're singing it. Next, you need an Ipod or any other music playing device, like an MP3 player or smart phone that has the song you want to sing, then put on some headphones and plug them into the device that has the song. That will help you sing with the music to make sure you don't go ahead or behind the song. Now you need a decent camcorder or smartphone to record the video. 720p is the minimum to record with, if it is not HD, most people won't listen to your cover. But full HD, 1080p is recommended. A good singing voice is also needed! Now, you can use the camera's microphone or get a better quality one.
Once you have all that, lets begin...
Step 1: Step 1
Take the camera and point it at you, put on the headphones and start the song. Start MOUTHING the words that you want to sing, don't actually sing it.
Step 2: Step 2
Now take that better quality microphone or the camera's microphone (if you use the camera's mic, use an online video conversion service to convert the video file to audio to edit it later on top of your first video of when you mouthed the lyrics), and start to ACTUALLY sing the song this time.
Step 3: Step 3
Now you should have a video of you mouthing the lyrics which you want people to see, a video or mp3 of you actually singing, and the original song without vocals. If you have a video of you singing, just convert it to an audio format later.
Step 4: Step 4
Now take the video of you mouthing the lyrics in the editor and add the audio file of you singing it. Now line them up so you look like your singing.
Step 5: Step 5
Now export it to a video file. Put it back in the editor and take the actual music to the song without vocals and line that up as well.
Step 6: Step 6
Now enjoy your new song cover!!! (also don't forget to upload it to YouTube!)