1. My compost bin smells and the contents are slimy.
This is usually the symptom of there being too much green organic matter in the bin, often grass cuttings as these are incredibly high in nitrogen. The solution is to add large amounts of dry brown material and give the mix a stir. Remember to always keep a roughly equal mix of greens and browns.

2. Composting is going very slowly or has stopped altogether.
This probably means the compost is too dry and little bacterial action is taking place. Try adding a bucket of water and/or some fresh green materials and giving the compost a stir.

3. There are fruit flies all around the compost bin.
These are not a problem for the compost