Your advisor is a professor whose job it is to keep track of your progress throughout college and to give you counsel on what classes to take to fulfill general education, major, and minor requirements. Colleges normally pick advisors based on, when you are a freshman, what you think your major will be, so that you have someone who can also act as an advisor in your specific discipline. As such, if you change your major from what you thought it was going to be, it is perfectly normal to change advisors. Yes, advisors are professors and therefore have other things to think about, like their classes and research, particularly if you are at a university. However, they have to devote some of their time to helping out their advisees.
Since advisors are an available resource, please take advantage of them. Your advisor can be a sounding board for any major academic decision you make, from choosing your major to going abroad for a semester. They can help you keep track of which requirements you have yet to complete, a particularly difficult task especially if you are trying to double major or do a minor. As someone from your discipline, advisors can also keep track of your progress and advise you to take certain classes to learn important skills and/or methodology. They can tell you about research opportunities in your field and help you with applications to graduate school and for scholarships and fellowships. They can even provide advice on your career plans, particularly if you plan to go into academics.
Because of the wide variety of benefits that come from having an advisor, it is important that you cultivate a good relationship with your own advisor. You should take at least one class with him/her so that he/she has some grasp of your current academic level, particularly in your chosen field. You should not hesitate to meet with or contact your advisor if you have a question. You do not necessarily need to flatter your advisor or anything like that. But it is best that you not anger your advisor by acting blatantly disrespectful or by showing no interest in your academics or his/her advice. He/she is there to help you, not to bother you.
Unfortunately, not all advisors are equal. Just as some academics are far better researchers than they are teachers, and vice versa, some advisors simply do not know how to advise very well. They may try to push you along a certain path without any regard for your personal interests or predilections. They may completely fail to inform you of any research or scholarship opportunities or even to keep track of your academic progress. Or they could just have bizarre personality quirks that make interacting with them extremely uncomfortable. In such circumstances, what can you do?
Well, so long as your advisor is not the only expert at your college in your field (which is particularly unlikely if you are at a university), then you can always switch advisors. Sure, you may have some uncomfortable interactions with your original advisor when you have to tell him/her that you want to switch. All you can do is bear it and try not to make him/her mad. Try to downplay any conflict and make it sound as though it is not the professor’s fault. Chances are that you will not have to interact with that professor much more afterward, but it is still best not to burn your bridges. If you are going into academia, that professor will be your senior, and you do not want your senior angry with you.
Another thing you can do is to take the initiative with your advisor and ask a lot of questions. Some advisors may just be too busy to think about helping you as much as you like without prodding. If you constantly ask your advisor about research and scholarship opportunities, your academic progress, graduate school, and requirements and whatnot, they will have to answer you. You will get a lot more from your advisor if you play an active part in your relationship, even if your advisor is good, so it can only help even more so if your advisor does not seem to be attentive enough. If your advisor still does not answer your questions often or to your taste, then please switch. Do not put yourself through unnecessary stress by dealing with a bad advisor for four straight years. Just remember that you have to do some of the work yourself. Your advisor is there to assist you, not to hold your hand. Yes, some advisors do that, but better to be diligent than to be disappointed by a busy, inattentive advisor.