Here is a step by step guide to answering these questions. I think that heading matching is the easiest task, so I always advise you do it first if you see it in the exam!
1) Have a look at the attached document http://www.ielts.org/pdf/115016_Academic_Reading_sample_task_-_Matching_headings__2_.pdf
2) With a heading matching exercise, the first thing to do is read the first two sentences of each paragraph and try to match any keywords / synonyms to the questions. Do this for each paragraph.
3) At the end, if there are any you still can’t match, then go back and read two more sentences.
4) Be quick! If you can match two keywords or an idea, you don’t need to read any more, so don’t! Remember, if you’ve read four sentences and you still don’t know the answer, don’t waste your time – go to the next question and leave this one.
Have a look at the first two sentences of each paragraph. I’ve underlined the key words that show you the answers:
A: The role of governments in environmental management is difficult but inescapable. Sometimes,
the state tries to manage the resources it owns, and does so badly
B: No activity affects more of the earth’s surface than farming. It shapes a third of the planet’s land
area, not counting Antarctica, and the proportion is rising.
Here, the answer isn’t clear, so I started reading the third sentence, and found World food output per head
C: All these activities may have damaging environmental impacts. For example, land clearing for
agriculture is the largest single cause of deforestation;
D: Government policies have frequently compounded the environmental damage that farming can
cause. In the rich countries, subsidies for growing crops and price supports for farm output
drive up the price of land.
Here’s the example:
E: In poor countries, governments aggravate other sorts of damage. Subsidies for pesticides and
artificial fertilisers encourage farmers to use greater quantities than are needed to get the
highest economic crop yield.
F: A result of the Uruguay Round of world trade negotiations is likely to be a reduction of 36 per
cent in the average levels of farm subsidies paid by the rich countries in 1986-1990.
Good luck – remember to give yourself one minute per question, and don’t overread – match ideas, be confident and move on to the next question!