I heard that it's good to use two colours of paper - you can make one layer with one colour and the other with other colour. This way is the easiest one for you to you know that the the thickness is continuous.
I found another one. I work from newspaper. I start with one paper square on an edge. Then I add squares in the circle around this one. I keep laying circular rows. And how do I know where I was already? I make one row by pieces with black and white text only and the other one by pictures.
It's quite easy because newspapers are doublefaced and you have more possibilities to choose from :-)
By the way this work is nice and comfortable. I got used to pouring amyl to the bottom of the dish and wet the pieces inside. Then I place it and stroke until all of the amyl squeezes out from under. The square leeches onto the dish and the surface is slippy and smooth ;-)