12 months is a difficult age to shoot.
It depends on the child. My first question is:
Are they crawling or walking?
If so, they will prove VERY difficult to 'pose' the way you want. I have found that the best thing to do is light the area, including the backdrop, and just let the child do their own thing in front of it. HOWEVER, the site of the backdrop and lights may well disconcert the child so judge it as you see fit.
The most valuable tip I can give is spend the first ten - fifteen minutes on the floor with the child with your camera still in the bag. Just play with them, get them to show you their best toys and interact positively with them. This will gain their trust and they will be more comfortable with you behind the camera.
To get them to look at you, a useful tip is to have a small bell or something, that can be fixed to your wrist somehow. Give it a jangle, they look straight at you and you hit the shutter.
Allow them their favourite cuddly toy to play with as well. That can often keep them still for ... well.... a few seconds at least.
Also enlist the help of the parents - get them to stand at opposite corners of your lit area and let the child run between them.
If the child is really not happy at all the fuss and lights and stuff, stick your speedlight on and let the kid play the way they want to, where they want to and with what they want to.
Miserable kiddie shots do not sell well, so be prepared to be controlled by the little mite for an hour - just as long as you get them to smile, cutely, with their big round eyes looking straight down the lens.
Oh and one more thing......
..... the VERY best of luck!