I don't have a battery grip and I don't think i would like the extra weight as I like to hike and just carry my camera out. Thanks for all the info though. The link to Ken Rockwell actually says not to run the batteries all the way down which I am not used to. Lol i used to be into RC cars and you had to run them completely dead before you could charge them again or the battery life got shorter and shorter.

Kyoshinikon is right the best place to keep it is in the grip :)tcole1983 do you use one by any chance? I use to but couldn't stand the extra weight any more for long extended hikes or time in the field so I sold it. The battery will have a charge for weeks if left on your desk I find. I have 4 extra batteries but one of the them is fake made in China and they all hold a charge well except for the Chinese battery which dies quickly especially in Liveview. It goes from full bars to blinking after 3 liveview shots! Real Nikon Batteries last for hundreds of shots though. You should make sure you have the proper plastic cap for the exposed terminals on the battery though it helps prevent wear and tear and prolong it's life.

I have 4 that I try to rotate between two bodies, grip, and charger but it doesn't seem to make much difference. With technology these days, I keep all of them charged. I mark the purchase month/year on them since they do loose some power over time. 4yr old battery I still get about 900 shots out of it but it does drain faster when it is cold.

I carry an extra battery fully charged while on a shoot. I swap the batteries (when opportunity presents, just like I swap my memory cards) when the one in the camera is almost exhausted (but it does not have to be 100% exhausted, since lithium’s don’t have the NiCad’s memory issue). I charge the exhausted one as soon as possible and keep it on hand for the next swap. I do not differentiate between the two batteries as the main one and backup one, but put them to use in alternate manner.

I keep it in my grip... :P You will find that with a grip you seldom run out of juice because if one dies you charge it while you are using the other and vicey versy. In this way I almost never have an empty tank and it also makes it hard to lose any of my batteries. Also If so-be-it I run out of juice on a shoot I can steal one of the batteries out of my D200's grip and the problem is solved... Additional backups are pocketed or in pouches clipped to my belt as well as the AA cartridge for my grip just in case I run out of all juice...

Im also use them till they expire 100%

As monty11 says, it's more as a rotate cycle.

I use my batteries until they get about a 20 % of charge in camera. Then I charged up the battery I have out of the cam, and change them. Then I charge the "old" battery for about 1 hour (that gets it to about half charge), and leave it on the shelf until next cycle.

This is without an event (trip, social...) scheduled, of course.

Saludos!

The lithium batteries that power Nikon's current generation of DSLRs will hold their charge fairly well. I keep my extra batteries charged up and in my camera bag and swap them out whenever the battery I'm using falls below 50%. Thankfully it's no longer like in the days of the D1 series where you had to bring your charger along with you even on day shoots!

You don't get yourself a back battery, but an additional battery and you rotate them so they get roughly equal use.

You may want to check this out kenrockwell.com/tech/batteries.htm as it contains far more detail about batteries and battery life that I can post here.
You don't say which body you have but with a D3 you'll get roughly 3000 images on a freshly charged battery.

I am hopefully getting a backup battery at Christmas. I was wondering what everyone does with their extra battery. Do you always keep the backup charged? Will the backup stay charged if it is left for an extended period without being used? I would obviously switch it out when the first one I was using died, but I rarely shoot enough shots in one outing to run through a whole battery. My biggest problem is having a partially charged battery when I go out and then running out half way through the day. I obviously want to run the battery all the way down before I changed it again and I see that as being my biggest use of the backup. Any thoughts on it or just good battery practices?