Essentially you must keep in as much heat as possible. One way is to make the pile a large one, although in warmer climes the heat comes naturally within the pile and requires little assistance. Plastic compost bins, or adapted receptacles, are much better than using ordinary plastic bags, are very sturdy and make a big difference.
The actions to take are fairly simple. Firstly, you need to make a layer of grass cuttings about 20 cm in depth. Next, spread a layer of shredded carbohydrate rich material,l such as newspaper or sawdust, over the surface. You can even use oatbran or such like if you have any stale cereal in the cupboard. A couple of small handfuls should be plenty. Now you need to cover this with a thin layer of soil. Approximately 2.5cm will provide an abundance of bacteria and will additionally absorb the water and gases which stop the compost making process. Continue in this manner until all of the grass cuttings are used, then cover the top to keep out the rain, or simply place the lid on the plastic compost bin.
Next time you mow your lawn simply repeat the process on top of the previous pile. A pile made in Spring or Summer can be used in late Autumn or the following Spring. If the grass has been treated with a feed and weed spray leave at least six months between placing grass cuttings on the pile and using the compost.
As well as grass cuttings I tend to add other natural matter such as vegetable peel or other similar waste. I try to avoid anything which contains seeds as these have the potential to sprout and grow in the compost pile. I also absolutely avoid adding any weed matter to my pile as they have the same reaction as seeds, which then defeats the whole object.