When I get my new iphone how long should I charge it before I use it?

Iphone 4s if that makes a difference.
How long should I charge it before I use it?

Wait till it's 100% charged. So leave it charging for an hour or so.

It should be charged when you get it so you shouldn't have to wait. But if not plug it in until it says 100% charged

One full charge before use

I believe it's recommended you charge it overnight.
Check your instruction booklet.

Charge it until its 100% full before you use it. This will prevent it from dying quickly in the future. Hope this helps!

Charge it to 100% and leave it for charging for about 2 hr