Standbye, shut down or turn off on a computer please?

I have had several different responses from my friends as to what is the best way to conserve & long term maintenance for a computer as far as to when it is not in use, I just invested in a rather pricey new one, my old one really did well, I had it several years and when I was done working thru the day I just put it back to the original screen off line and it basically put itself to bed, all I had to do in the morning was touch the mouse and my screen came up with the icons I wanted to choose from, I eventually got a virus from not updating my Norton quick enough that killed the hard drive over time, so, now I am much more careful on that end but really wonder as to what mode it should be in at night when not in use, I know how smart you guys are and that we have many people in our community that are absolutely the best in the world, please give me your advise and it is so much appreciated. Thank you from the bottom of my heart, and probably my pocket book, you guys are all wonderful