To answer your question.. you should ask questions of agents before you "hire" them to work for you.. It's really no cost to you as the buyer.. Do you want someone in your corner during the process? You really don't know what you don't know when you are starting out.. Can't really hurt to find someone that can help you and add value to the process. Right? When you sign the buyers agent agreement just ask how you get out if you are unsatisfied with their services. Their is a section that outlines how you can terminate the agreement.
There are ethics standards that licensed agents are held. From the perspective of the buyers agent wanting to keep the price high... wouldn't you want to make a % of a deal even if it is a lower sales price and be a valued source to a client? Real Estate is a people business and if you are not helping and adding value to people that will be directly reflected in your success. To be truly successful you should have a larger # of people that you can lean on that can provide advice and guidance.
Good Luck!