So many questions! This important decision should be made with much thought and consideration. The more homework you do to investigate your choices and educate yourself, the more capable you will be in making an informed decision. It is never too early to start thinking about graduate school. Speak with a career counselor, instructors, advisor, and colleagues. Each can provide you with information and personal experience that will be helpful in your decision-making process.
Your decision to attend gradate school should be based on a strong vocational interest, a passion for further knowledge, and a desire to increase your income potential -- not to avoid getting a job or because you're not sure what you want to do. To work or not to work prior to graduate school really depends on your situation and field of study. Some graduate programs strongly encourage people to have work experience. You should explore what is expected in your field of study.