First, you have to do a ton of research on each agent before you contact them. The internet is full of scammers looking to prey on someone desperate for a book deal, or amateurs who will be a waste of your time (and possibly money) because they call themselves “agents” but don’t really know what they’re doing.
Then, after you do careful research to find a legitimate agent, the next step is finding one who thinks you have an amazing book. Even then, there’s no guarantee of a publishing contract. Just like authors, agents typically get a number of rejections before they find a publisher who shows interest in your book.
If they do get your book accepted by a publisher and get you an advance for your book sales, it comes at a cost–15% of all your earnings.
So if you aren’t set on getting published by a company that REQUIRES an agent, a better option might be getting published without an agent. There are tons of reputable medium and small publishing companies out there, and more and more publishers are loosening their grip on the reins to allow un-agented authors to contact them directly–cutting out the middleman. Even big companies dabble with submission periods of bypassing literary agents to find talented writers.
Although small publishing houses don’t have the same clout with retailers or the same resources for marketing and publicity, most still have talented editors, designers, and passionate professionals for publishing great books.