When you finish a picture, mask it off as if you were going to mount it (I just use sheets of cartridge paper to do this). At the bottom you will see that there is going to be an area either left or right that you could use and put your signature in. If it’s a dark area then you could use a very sharp white pastel pencil to sign with.
Note: I always use the same medium as the painting to sign with.
With the “mount” on the picture, you can judge about a quarter of an inch up from the bottom (about the same from the side, although it doesn’t matter so much here). If you don’t use this mounting method then you when you come to frame it very often you have to frame too much of the picture because you have put the signature too far down.
Some people may choose to date their pictures too, I personally do not do this as I was told many years ago if you want to put the painting into an exhibition and it doesn’t sell and so on, then people will know it’s an old picture and this could possibly have a detrimental affect to the picture itself. This is of course only my opinion, it’s entirely your choice.
Do you date your pictures? Let us know in the comments below.