Publishers will tell you...that every manuscript which reaches their office is faithfully read, but they are not to be believed. At least fifteen out of twenty manuscripts can be summarily rejected, usually with safety. There may be a masterpiece among them, but it is a thousand to one against.
Choosing an agent is a lot like choosing a hairdresser. [I currently don't have an agent or a hairdresser.] If you know a bunch of writers and most writers do because who else is home all day?) ask the successful ones who represents them. [In reality, writers with agents hate to be asked this.] If you don't know any writers, look at books by authors you admire and see which agent the author thanked in the acknowledgements. Send five to ten of these agents a resume, cover letter, and proposal for what you're trying to sell (it's imperative that the prospective agent knows that you have a money-making project in mind). Interview the agents who respond positively and pick the one you like best. If no one responds positively, send your stuff to another five to ten agents. Don't take it personally. Think of it as practice in handling rejection. (Believe me, you'll need all the practice you can get.)