Pompei

We had a guided tour of Pompeii and there was a counter to pay to join one at the site. I thought it was worthwhile.

There were idle guides hanging out around the ticket counter when we went.

Like others have said, there are generally guides hanging around the entrance, very knowledgeable and modest cost, I understand, available for 2-hour tours. You can “interview” some to decide whose personality clicks and be sure you can easily understand their English. I did not use one, but wish I had. Not only do they know the site and history very thoroughly, they also know which areas, streets or buildings might be closed that day for reasons of renovation, etc. No written guide or map would indicate that.
Also, when I left Pompeii a few years ago, at the train station shop, I bought a great highly illustrated 8 x 10 paperback book entitled “Pompeii: 2000 years ago and today.” Published by Bonechi Edizioni. Price was 12 Euros at the time. Can be both an illustrated guidebook while there, and a souvenir for later. I have it in my hands at home right now. The great feature of this nice book was that along with text, diagrams and many photographs of the ruins at present, it also has really excellent color drawings of what various buildings would have looked like 2000 years ago, inside and out, with people using them in their daily lives. Really brings the ancient stone ruins to life. I wish I had bought the book when arriving and used it during my visit.

You can use this-- https://www.ricksteves.com/watch-read-listen/audio/audio-tours/italy

( scroll to the bottom)

On our shore ex, our group of 6 ended up "picking up a guide" upon entering. We really lucked out! He even showed us the National Geographic magazine where he is a featured Pompeii guide. A few years later we were visiting again with other friends and I sought him out again. He met us on the train platform and helped us store our luggage for a few hours en route to Sorrento.

Coincidentally, RS now lists him as a Pompeii guide as well. He may be harder to book as a result. He'll also do Vesuvius tours.
Here he is depicted with RS and his National Geographic spread. He speaks excellent English as he lived in NJ for a while years ago.
Antonio Somma
http://www.pompeitour.com/tours/pompeii-guide/

I agree with joe32f.... We actually had a Mondo Tour guide - booked through www.sharedtours.com for a Rick Steves rate - that lasted a couple of hours. But then we continued using Rick's audio guide. Some things have changed since he recorded it, but he provided insight the live guide didn't.

Take water bottles - you can refill for free around the site. Wear a hat, and use sun block if you're the type who burns. There is absolutely NO cover in the archeological area.

Oh, and wear good walkking shoes. There aren't too many level spots there, either.

Adding to the topic of walking shoes: It's not just an issue of heat or blisters. The polished Roman paving stones are uneven, and someone with the slightest weak ankles or knees could easily suffer a painful twist when stepping on a wide crack or a depression or a chariot rut. Watch where you are going.

We prefer to tour on our own, but when we went years ago, the then-current Rick Steves book was already out of date. Certain Roman roads had been closed to regiment growing tourist loads, costing us a lot of extra walking when we thought we had our Walking Tour scoped out for us. I'm not urging you to hire a guide, it's a matter of personal preference. The key is not to have some artificial time-limit on having to rush out of the place for your next three scheduled events of the day.

We were there about 10 days ago (took train on our own from Rome). I had the same questions, and my family decided to use the RS audio tour. If I were to do it again, I would go with a guide--probably Mondo for economy. As others have said, the place is HUGE, and it is very easy to get turned around; although some areas are numbered, the RS audio tour uses different numbering, and some of the spots were closed. If it is hot, the last thing you want is to retrace your steps if you are lost - which we did. One other recommendation --- buy your entry ticket in advance, even if it is the night before you go: the regular line (which we were in) took about 30 minutes at around 10:30 a.m. The "on-line orders" line had zero wait. There were guides hovering everywhere near the entry, but I think it would have been challenging to choose one on the spur of the moment. Enjoy your visit -- it's fascinating and 2 hours will just scratch the surface. We were hot and exhausted after 2.5 hours, but we loved it and would have liked to spend more time, if it had been cooler.