In writing a compare and contrast essay often the hardest task is selecting the right topics for your work. In most cases, it makes sense to compare and contrast only two items or topics. This makes it easier for both you and the reader. It's much simpler to create and understand an argument or presentation that requires less memory, and one that reduces confusion. This can be done by limiting the comparison to the least possible number of items, i.e., two items or topics.
However, there may be times in which the subject matter will require that you compare and contrast more than two items. For example, if you are comparing the best internet search engines or smart phones, the situation may require that you include all items that are relevant to your comparison.
Generally it is always best to pick topics that you know something about. This will usually make your work much easier. However, in many cases, you will be assigned subjects or the subject matter of the course is not something in which you are familiar. In these cases, it pays to find topics that spark some interest within you. When you have an interest in the subject matter, it again often makes your work much easier as you are motivated by the information you are studying.
A good way to start is make a list of possible topics that interest you, and/or that you have some knowledge about. When you have made a list that seems satisfactory to you, begin to analyze the topics on your list. You should consider things like the length requirements of your essay and the amount of time you have to complete the work. Some topics may be relatively easy to research with plenty of information available, while others present a more difficult task. For example, if you decide to compare dinner tables, consider how easy or difficult it will be to obtain information on dinner tables. Often, depending on the requirements of the essay, you will be wiser to pick topics in which much information is readily available.
One way to quickly assess your choices is to conduct cursory searches on the topics using major search engines like Google and Yahoo. If you are able to quickly find relevant information, you can decide whether the topics will be manageable given your essay length and deadline requirements. After some work, you should know which topics are acceptable and can be included in your final list.