Anil sent in an interesting question asking
If there is a problem how do Muslims decide what to do?
First of all Muslims look in the Holy Quran. There may be a specific instruction or prohibition such as fast or perform Haj or do not drink or do not back bite etc. Failing that there may be general principles laid down in the Quran which a Muslim can use to find what to do such as the instruction in the Holy Quran which says that it is only lawful for Muslims to eat those things which are good for them. Smoking is not good for us so although the Holy Quran does not have a specific instruction prohibiting smoking this instruction can be used to show that smoking is prohibited by Islam.
If there is nothing in the Holy Quran then a Muslim turns to the practice of the Holy Prophet Muhammad (pbuh). This is called the Sunnah, or the example. There are many things which are laid down in the Holy Quran in principle and the Holy Prophet showed by his practice how this is to be put into practice. For example the Holy Quran tells us to pray and the practice of the Holy Prophet Muhammad (pbuh) shows us how to pray.
If there is nothing in the practice of the Holy Prophet then we look at his sayings called the hadith. For example, the hadith tells us that if we are selling something we must point out the bad points of our product as well as good. In another example, Muslims asked the Holy Prophet how to pray in those places where the day or the night last for six months. The Holy Prophet (pbuh) said that there is nothing magical about the sun which makes us say the early morning prayer 1.5 hours before sunrise and mid-day prayer when the sun is directly overhead etc. This was just a convenient means of fixing the time which was visible to all. So when people see the sun directly overhead they know it is time for the mid-day prayer. He then added that if this is not possible then the community should gather together and decided on some other means of knowing when to gather for prayer.
If a Muslim does not find any guidance in any of the above sources then he uses ijtihad. This is using one’s own knowledge, understanding, commonsense etc to try and find a solution to a problem. Muslim scholars have been doing so down the centuries.
Another way is the ijma of the community. This is the consensus of the whole community. So Muslims gather together and discuss a problem and the different options open to them and then agree upon a solution or course of action.
Modern day government has borrowed these techniques from Muslims. Look at the way laws are made in your own country and you will find these Islamic principles being used to formulate laws.