What is your current lighting setup? I know it may sound super obvious, but I have found that my cameras often have trouble focusing if my room is too dark. It's all just shadows and blah, which means I end up with blurry images and a TON of noise, which also seems to degrade the quality of the footage. Investing in my lighting and learning how to utilize the lighting properly was the best thing I did to improve my clip quality, both for DSLR and camcorders alike!
Also, learning how to properly white-balance my shots saved me a LOOOOOT of time in the later editing stages!