Suggestion for the folks, read the book License to Deal. You get a glimpse of how competitive the business is, and how problems usually arise from the agents themselves vying for the same clients. And remember, that if perhaps you and your son DO make an agreement with someone and change your minds later on, that may cause problems.
This sometimes happens when a relatively unknown suddenly rises to the top and has more options. Or a player out of HS works with an advisor for years and goes with another agent thinking that he can get him more money. That's why, IMO, sometimes it's good to get advice and not decide anything until closer to draft day, for some that may be senior fall, for some not until late spring. All situations are different.
As far as some of the questions or things being discussed here, write down a list. DO NOT BE AFRAID to ask those questions of the advisors who might call upon your son. Remember, just like the coach courting your son, if it doesn't feel right, then look further.
Some people go out looking for advisors, an agent (not his) told my son once that he gets over 300 requests a year, but takes only a few. Most advisors (including those contacting mine in HS) that will make contact with players are those looking to get into the business further and need clients and need MONEY. The more milb players he gets signed the more $$ he makes. If your son really has the talent, those who do not need the milb bonus dollars will be knocking on the door. That is a strong indication of where your son may fit in the scheme of the pro draft. My philosophy, if your son's advisor needs his bonus walk away. It's not taking the bonus, but what that agent can do later on for your son for teh bonus $$. If he can't do anything, has no MLB experience, cannot even deal with MLB, why the need for his services, your son will undoubtable make a change later on, so essentially you wasted that money.
Remember, the good agent gives advice freely, hoping that your son will use his services later on as an agent, and someday, maybe even after sticking it out 0-8 years together he will make some money, only if your son does.