The best rules of thumb, or general guidelines, depend on the exact topic. For example, in cleaning, the rule of thumb is often said to be to clean from the top down. A good rule is based on common sense and tips that have been shown to be successful when doing a certain task. The top-to-bottom cleaning guideline is based on the fact that, if the floor is cleaned before a higher surface such as a table, it can become dirty again from debris falling from above. Rules of thumb can be applied to any industry or task.
The process of job hunting has many guidelines known to be successful. For instance, maintaining comfortable eye contact with a prospective employer is said to be an important rule of thumb during a job interview. Other well-known rules for job interviews are having questions prepared, offering a firm handshake, and never being late. Following these guidelines can often help someone get hired from a job interview.
In general, the best rules of thumb consist of tried and true methods of doing something. People have different ways of doing things and still achieving success, but a proven rule usually brings success to just about every person who tries it. For instance, in sewing and woodwork, people are advised to always think carefully before cutting fabric — the saying is to "measure twice and cut once." This rule of thumb works for everyone since, once the fabric or wood is cut, it can't be made bigger again. Making sure that measurements are correct and accurate can prevent materials from being wasted.
Guidelines like this can help stop big mistakes. They advise against what a person's instinct or emotions alone may tell them when those things shouldn't be applied to a task. For instance, driving a car should be about defensive operation to prevent accidents. Studies have shown that many drivers experience the instinct to speed up in foggy conditions, but the best advice when driving in fog is to slow down, since visibility is severely limited.
A rule of thumb often becomes common knowledge if it's a popular way of doing something. For instance, the idea of inserting a straw or toothpick into the center of a baked cake to see if it's done is one of the best well-known guidelines because it works very well. Other good rules when baking cakes are to use the center rack in the oven and frost the cake only after it's completely cooled.