Commas and apostrophes are not there just because it feels good. They actually mean something. Just like the difference between "accept" and "except," there is a difference between the meaning of many sentences when you make the decision to put the comma in or leave it out. Apostrophes are the same. "The boys' book" means that the book belongs to several boys, while "The boy's book" has only one owner. Your question was about how to minimize the errors, and there is an answer, although it is not simple and won't be fast. First, you need to learn the differences in meaning which placement or omission of commas and apostrophes signal. You can do this with textbooks about writing skills or with style manuals. Take a look in a brick and mortar bookstore or check at a library. Once you know why "My sister, (comma) who lives in Vermont, (comma) married young" doesn't mean the same thing as "My sister who lives in Vermont married young (no commas), then you must watch what you are doing when you write. Make sure you are saying what you mean. If you mean "it is," then you use the apostrophe (as in "It's too late to go out,") but if you mean "belonging to it" then you don't (as in "The dog bit its tail.") Correct use of commas and apostrophes is a matter of knowing the meanings and developing the habit of paying attention.
Added 10/9/2011 3:59:41 PM