Short answer, no. I never have unless it was recommended to me by another individual. I usually buy games based on the appeal and previews, and maybe if it's clamored enough by fans. Otherwise I stick to franchises anyway and make all kinds of blind purchases.
I didn't even watch any videos or look at any ratings or have much of an idea at all what the heck DeathSmiles was, but it looked like a hori-shmup and that was good enough for me. Ended up being one of my favorite all time games. I bought DoDonPachi Resurrection because it was developed by CAVE. I also played other games in the DoDonPachi series. I don't like it as much as DS, but I still think it's a neat game, and don't mind having shelled out the money.
I bought WarioWare Inc.:Mega Microgame$ in 2003 because it looked funny and appealed to my short attention span while I tried it at Best Buy or something. Bought it right off. Same thing for Rhythm Heaven (DS), plus I knew it was done by the WW team.
That's just an example of my usual reasoning. If it's cute and has an art style I can get behind (or draw myself <_<), I'll play it. That's usually how it goes.