Uploading high quality videos to YouTube?

Okay, so my friend and I have a YouTube channel (Tortia AndSalsa) and I record with my Nikon camera. It's a awesome camera that takes great pictures and pretty great video too! But what I have noticed is that the quality that gets uploaded to YouTube is completely different then the quality of the original video that I have on my computer… Is there anything to do to fix this?! If so… Please let me know!

Do you format or edit the video in any way before uploading? You may save it in a different aspect ration or player size, which may reduce the quality of the video.
Other than that, did you wait for YouTube to fully process your video? HD quality video takes time to process after uploading, usually up to an hour for every 30 minutes of video…