Changing default fill when creating a shape in a new layer.

Hi everybody,

I have searched high and low, but cannot find a solution to this problem. I'm quite new to Photoshop, so please forgive my ignorance incase this is something very simple that I have overlooked. 

When I create a new layer, and then draw a shape (usually a square or rectangle) on that layer, it automatically by default fills it with a black and white gradient fill. I would like it to fill with a solid colour. My question then is how do I switch from the gradient fill to a solid, and make this the default setting?

By the way this only happens when I draw a shape on a new layer. If I draw a shape on an existing layer then the default setting is a solid fill. Thanks in advance for your time and help.