Getting the best Quality with my miniDV camera?

Okay, I have a Sony DCR-VX100. I know, ancient. I want to try and squeeze the best quality possible from this baby until I get enough money to upgrade to HD, though. One thing I noticed is that sometimes the final image on my computer is really grainy looking, but sometimes its not. Should I shoot with more light? Should I try and get a better quality miniDV tape? If so, what brand would be best? Is the program I use to transfer the DV onto my computer affecting the quality at all? Do some programs retain better image quality? Help, please!