First it should be pointed out that in terms of preventing plaque build up and gingivitis the differences between different toothpastes is very small. Mostly it is the toothbrush and our technique that makes the difference!
When choosing a toothpaste use common sense. Aside from the obvious fact that it is not the best choice to buy one made in China at the moment, I believe that less is more. I believe in using toothpastes with fluoride. Choose one that doesn't make multiple promises. A Whitening, tarter control toothpaste with other special properties sounds like a great idea, but the truth is that people have sensitivities to some of the ingredients and the more that are included, the greater the likely hood that you may have a reaction.
When I purchase toothpaste for myself I find a 'basic' version, that doesn't promise whitening or tarter control. It can be hard to find on the supermarket shelf, since the 'fancier' toothpastes cost more and the supermarket makes a bigger profit from them. Do not get roped into thinking that spending more for a product promising additional benefits will actually get you a better toothpaste!