As with many other aspects of gardening, this one seems to be easy as long as you don't get deep into details. 

What to compost and how? 

How, if at all, can you prevent producing unpleasant odour of decomposition? 

How much time does it take to produce compost and why produce it at all? 

Below we explain a few most important aspects on composting that should clear the issue a little:

  1. The first and foremost thing for all to remember at all times: A COMPOSTER IS NOT A RUBBISH BIN!
    Seeds and roots of weeds do not decompose that quickly in a compost pile. When distributed on flower beds along with produced compost they can bring more problems than benefits. Similarly, vacuum cleaner bags, tissues and animal excrements should be disposed of in the correct waste bin, in accordance with applicable rules for waste segregation.
    For composting you certainly should not use peelings or parts of fruits and vegetables exposed to high concentrations of pesticides (e.g. citrus fruits). There is a risk that the chemical compounds get to composting mass, and with that to your private crops. Coffee grounds, used tea bags or paper filters contain significant amounts of zinc and copper, so they're not a great material for composting either. The same you can say of ash that may contain high amounts of heavy metals. Also avoid leftovers of boiled food, as they are a risk of salmonella and they attract unwanted company, e.g. rodents. 
  2. THE RIGHT COMPOSTING MASS IS THE KEY TO SUCCESS. What and how to compost then?
    Firstly, the most optimal mix for correct composting are two parts of dry material for one part of wet material. Dry materials (structured) include: shredded branches (shreds, chips, cut-offs), pieces of bark, dry leaves, saw dust, straw, cut branches of hedges and garden ornamental plants. Wet materials (soft) include: flower remainings of balcony and flower beds, fallen fruits, residues of crops, wastes of raw kitchen plants, fresh leaves, cut-offs from bushes and mowed grass. 
    Given optimal conditions, compost is mature within approx. 1 year. However, when prepared in spring it usually gets mature near end of the summer (thanks to higher temperature and humidity). Compost prepared in autumn will stay virtually unchanged until spring, because in freezing temperatures all organisms responsible for decomposition are inactive. To speed up production, you can additionally cover the compost with black foil, which holds humidity and warmth. 
  4. How to tell when the compost is ready?
    You will need pitchfork for the purpose. Remove the first, top layer to the point, where you see organic pieces less and less often. Ready compost should be brown, brittle mass (breaking apart in hands) and smelling earth. It is harder to spot an earthworm in mature compost. 
    It is definitely not true! Bad smell comes from anaerobic decay bacteria that cause fermentation. There are two situations, when it can happen: when you put too thick layer of wet material for composting (this layer does not allow oxygen to penetrate deeper) or when the composter is made of e.g. plastic and has no ventilation. This is why it is so important to flip the compost through with fork. It allows to mix all material and aerate deeper layers of the compost. 
    Compost is very valuable material. It allows to save money on fertilizers, substances that improve soil quality and the ground itself. Additionally, it helps to dispose of green wastes. It contains nutritious material valuable for plants, which use it for correct growth.