Your camera can shoot 1080p I believe. So make sure you're in that setting. As others stated, make sure you have enough light (natural light is best) to get quality shots. You're vlogging, so you're probably moving a lot. I would suggest getting some sort of stabilizer to smooth your movement.
Secondly, in the post editing stage...make sure your project settings match what you shot. So if you shot 1080p @ 30fps, make sure your program is also set in that setting.
If you're using Sony Vegas, disable the resample (to do this I think you right-click your clip > properties > disable resample). Do this for all clips.
Lastly, when you render, be sure you render in 1080p HD using variable bit rate. You may have to tweak the settings until you find the right one you like.