Never put diseased plants, meat, fish, fat or other cooked foods. Any woody materials should be shredded before added to the compost bin. Also avoid adding any perennial weed roots or annual weeds that are setting seed, as these may survive the composting process and then you will spread them around your garden along with the compost. If you still want to add them to your compost, then let them first to rot in a bucket of water. Otherwise just throw them away or bury them deeply in a specially prepared trench.
You can pile the composting material in a heap but for best results it is better to build or buy a compost bin. The bigger the better because the greater the volume, the more quickly the compost will break down. A bin holding 1 cubic meter is ideal. If you have a large garden that produce a lot of waste then is a good idea to build 3 bins side by side. This way one can be filled while the second is rotting down and the third is being emptied of well-rotted compost.
The simplest compost bin that you can build can be made using cheap, pressure-treated fencing timber or by nailing four flat pallets together. Make sure the bin is up to 1 m square and deep in order to have a quicker result. Pile your garden and kitchen waste into the bin making sure that the layers of one material are not too thick. Grass clippings will not rot down if the layer is too thick because air cannot penetrate it. As dry materials you can add old newspapers and straw.
Keep the compost bin covered with and old mat or sheet of plastic. This will help to keep in the heat generated by the composting process and will also stop the compost from getting too wet. After a month turn the content of the compost bin with a fork to let air in and to move the outside material into the center of the bin. This will speed up the composting process. If you have several bins it will be easier to do this job by transferring the compost from one bin to another.
When the bin is full you can use it as a raised bed. Cover the surface of the compost with a layer of soil and use it grow marrows, pumpkins or cucumbers. If you are not going to use the compost soon just keep it covered with plastic or an old piece of carpet until you need it. You will know that is ready to be used when you will find in your bin a sweet-smelling, crumbly, fibrous compost. This should happen in just few months over in the summer and around six months in winter.
If the compost does get too wet, this will slow down the rotting process. In this case you can empty the bin completely and then put the composting mixture back while adding and mixing in as you go a dry material, such as shredded newspapers.