Hopefull I can help
The way I did it was to list all my case studies and put next to them whether they were Rural/Urban Socio-economic/poitical/environmental and MEDC/NIC/LEDC. This isn't the only way to do it, but I find it to help. By this method you can also create match-ups e.g. overnutrition (USA) vs undernutrition (Somalia). So here's my lists of Case studies:
Obesity in China - Urban, Socio-economic, NIC
China's Food Insecurity - Rural and Urban, socio-economic, NIC
Famine in Somalia - Both, socio-economic/political/environmental, LEDC <---this one's good cause you can pick and choose what you wanna focus on e.g. for socio-economic factors you can talk about the food prices rises of 2008 (i think), political there's political instabilty the sort of sets the tone for entirety of Africa as well as Al-Shabaab (terrorists) who shut down food supply routes for aid organisation. For enviro you have erratic rainfall leading to drought and therefore famine etc.
Pests (locusts and stuff) - Rural, Environmental, MEDC (USA)/ NIC (China)/ LEDC (Any African country, I prefer Ethiopia)
Ethiopia Famine - Rural/Urban, Environmental/Socio-economic/Political, LEDC Remember for that Ethiopia's famine was mainly down to erratic rainfall, but you can also talk about % of national budget spent on war instead of more appropriate technology for food production or how pressure is put on the nation from migrants escaping famines in places like Somalia.
Eritrea - Urban/Rural, Political/Envrio/Socio-eco, LEDC. In my class we were taught the case study of Ethiopia and Eritrea as one because of their military history, so don't be afraid to condense the two. You'll see a trend that many of the African case studies have a mixture of everything leading to their food insecurity.
Cattle Ranching in the High Plains, USA - Rural, Socio-economic and Enviro, MEDC. This case study outline how Americans have reached a state of developement in which they can afford to use inappropriate farming techniques on what should be used for arable farming, thus creating my next case study.
The US dust bowl - Rural, Environmental and socio-economic, MEDC. Not a recent case study (It occured during an 8-year long drought between 1931 and 1939) however you can mention it's historical importance as it came about due to inappropriate farming methods.
Kalahandi Syndrome - Rural, Socio-economic and political, NIC and LEDC. This is the idea that farmers grow cash crops to satisfy the global markets rather than feeding themselves, usually become they have to make money to pay for the land that they are farming and living on. Originating in India, if you do some research you'll turn up some dark stuff such as mass suicides over the whole event. Great case study as it outlines the how money can often be considered as more important than food.
Burkina Faso Famine - Rural and Urban, Enviro, Political and Socio-eco, LEDC. Another African case study which has all the regular features of political instability and erratic rainfall. However, this famine (April this year if I recall correctly) was partly due to the loss of jobs in the fishing industry in the Ivory Coast leading to a decrease in funds returning home so the poor couldn't afford staple foods.
The Sahel - Rural, Environmental, LEDC. The Sahel is the region just outside of the Sahara, countries like Burkina Faso and Mali have part of the Sahel within their borders. The Sahel often causes desertification and harsh growing conditions with nomadic pastorialists roaming and putting pressure on each country they pass. More desertification than anything else, but it's worth putting here just for the future.
The Great Green Wall of Africa - Rural, Socio-economic, enviro and political, LEDC. This is a huge project involving 11 African nations attempting to construct a wall 7,775km long to keep out encroaching Sahara sand. Similar to following case study.
The Great Green Wall of China - Rural, Socio-economic and enviromental, NIC. The original guys behind the green wall concept, aims to stop encroaching Gobi sands from spoiling rural farmlands which China desperately needs. Grab yo'self some reseach!
Cuapa Kokoo Fairtrade Co-operative - Rural, Political and Socio-economic, LEDC. This case study outlines the importance of free trade in bringing development to Africa, and thus helping to resolve food security. This case study is in the A2 book so give it a little look and keep it in mind just incase you need a solution. Be aware however that free trade is under criticism as a form of neo-colonialism (former world powers exerting influence over LEDC's) and as such it may not be as great as it sounds.
Green and Gene (GM) Revolution -Rural, Socio-eco and enviro, MEDC and NIC (GM) and LEDC MEDC and NIC for green rev. The Green revolution (1960's) and Gene Revolution (1990's) explain the attempts to create advances in yeild from crops and farmlands. Be aware the the green revolution mostly passed Africa by and GM crops are often too expensive for African farmers to afford. Should both be in the A2 book. Also be aware of the plans of a new green revolution for Africa (AGRA) funded by the Bill and Melinda Gates and Rockerfeller foundations.
Women and HYV's - Rural, Socio-economic, NIC. This case study outlines the importance of taking local decision making and tastes when attempting to apply solutions to food insecurity. Focusing on India, it explains how farmer's rejected High Yielding Varieties (HYV's) of rice because of its poor flavour and cooking qualities, not to mention how researchers overlooked the key role of women in rice production.
Golden Rice - Neither, Socio-economic, MEDC. This case study outlines how GM can solve common problems within the population. It foucses on Golden Rice which seem to be a solution to the common Vitamin A micro-nutrient deficiency. It outline strengths and weaknesses of the plan. Research this, it's definately worth keeping just in case.
Desertification in MEDC's - Rural, Socio-economic and envrio, MEDC. This case study outlines how MEDC's can fall victim to desertification (the USA for instance) without the aftermath of famine. Perhaps not so useful for this exam this time, but we'll keep it here for future reference.
I hope this helps, if you need anymore i'll do my best to find some or if you need anything explained i'll answer A.S.A.P! I'm taking the exam on the 19th as well so good luck to you all!