These four papers should get you started: the first two provide the theoretical framework, the last two are case studies from Mexico and South Africa, to give you a sense of the variance one has to deal with...
Roy, A., 2005. Urban informality: toward an epistemology of planning. Journal of the American Planning Association, 71(2), pp.147-158.
Watson, V., 2009. ‘The planned city sweeps the poor away…’: Urban planning and 21st century urbanisation. Progress in planning, 72(3), pp.151-193.
Lombard, M., 2014. Constructing ordinary places: Place-making in urban informal settlements in Mexico. Progress in Planning, 94, pp.1-53.
Kamete, A.Y., 2013. On handling urban informality in Southern Africa. Geografiska Annaler: Series B, Human Geography, 95(1), pp.17-31.