Though the scientific method has many versions dating back hundreds of years to Ibn al-Haytham (Alhazen, 965–1039,) the most popular version is the following:
1) Define the problem by asking a question, for example, "How do I get from Providence RI to Seattle, Washington in the cheapest and fastest way?"
2) Do Background Research, for example, decide how many different possible ways to go there.
3) Construct a Hypothesis, for example, "I think that the plane is the cheapest way to go."
4) Test Your Hypothesis by Doing an Experiment, for example, call the airlines and find out what prices they charge, including what other transportation methods charge.
5) Analyze Your Data and Draw a Conclusion, for example, write down all the different methods and rank them by price and time spent in travel.
6) Choose the best possible solution, for example, make a reservation by purchasing a ticket.
Though there are many other versions, some longer and shorter, the scientific method can be used for almost all of our daily decisions.
As indicated in answer above, meaning of scientific method may be interpreted in different way. At one end of the spectrum, it could mean to be a rather elaborate, step by step way to conduct scientific research, which involves defining and testing hypothesis. One such method is described in the answer above. On the other end of spectrum, scientific method may be interpreted to mean simply a method based on use of rational thinking.
Depending on the nature of task on hand, it may be wise to use different versions of the scientific method. For major decisions of our life like choosing a career, it would be wise to use some structured and elaborate method, however using such method on every occasion will not only become counter productive but also, will be unjustifiable by scientific reasoning.
In management we sometime talk of principle of bounded rationality. Stated in simple words, the principle of bounded rationality refers to the limitation in use of rational approach and the need to limit the use of rational approach in line consideration of time, information and cost of rational approach. For example you would not like to use a very elaborate rational approach in deciding the colour of shirt you wear on a Sunday morning.
Then there are occasions when it is best to just follow your instincts or habit - for example in deciding the brand of toothpaste you buy.
There are still other methods when it is best not to bother about rationality or scientific approach at all. These are matters of personal likes and dislikes. These may also include matters relating to personal relationships and listening to your conscience. Galileo was a great scientist, and it would gross arrogance on my part to imply in any way that his approach in life was not in line with the best scientific traditions. But, I tend to believe that his decision to embrace death rather than accept that his scientific theories, was very much base on emotions and personal beliefs, rather than any scientific analysis.
So in sum I will say that the best way to use scientific approach in life is to be rational, and use information and analysis only to the extent the time, cost and benefit of such approach are justified by the expected benefits. Also, there is nothing wrong in being irrational sometimes. They say:
A little foolishness now and then,
is relished by the best of men.