Travel Agents

I have never used a travel agent before in my life, I don't even know how they work. Can you meet with a bunch of them to price things out before choosing who to go with? Do you pay for their services? How much would it cost? I am totally 100% clueless as to how anything even works, so any insight would be appreciated.

I worked with a travel agent in 2004 because it was the only way for me to get to Greece because the Olympics had everything sold out and he was awesome. When I wanted to come home a week early he made the impossible happen which made me really, really glad I'd gone with a travel agent. At a layover in London everyone's flights were overbooked and cancelled and I was told that I could have to wait up to a few days for a flight and he made it happen for me within a few hours! Unfortunately, I had to spend the night there first in the airport before I could get in touch with him.

I didn't pay a fee, I assumed the price I was quoted included whatever they marked up.