Tour of Catacombs in Paris

I've been down there 3 times.

You don't get to "wander around". There is a 'set path' that you go on, going from room to room and down passages in between. You can go as slow or fast as you wish, but generally takes 45 min to an hour. Most people go without a tour.
I'm not into detailed history and I was fine on just reading up in advance and looking at pics on Google and looking up the French to English translations of the few inscriptions (stuff like "Here lie the innocents that died in 1740").
Nonetheless, there are tours and there are reservations, which you can look into here:
http://www.viator.com/Paris-attractions/Catacombs-Les-Catacombes-tours-tickets/d479-a590?pref=02

Due to two recent movies filmed down there, it has gotten VERY busy and popular lately. Look up the hours and either get there very early in the morning or get a reservation and/or set tour time.

The hardest part is finding it. It's on a large "traffic island" at the busy intersection at Denfert-Rochereau

We went in October. The first attempt was on a weekday around noon, the line was so long we estimated the wait to be about 3 hours, so we left. We went the next morning about an hour before they opened and we only waited about an hour and I rented the audio guide which was really informative. I recommended that you make a reservation online for a time slot so you do not have to wait. I did see tours in there but they seemed a bit slow moving.

The visit is tightly controlled - you can't wander around anywhere, can't touch anything, just follow the route. It's nothing like the movie, if that's what anyone is expecting.
I would recommend buying the cheapest tickets and doing some research before you visit the Catacombes. Then buy the English version audio guide and use that during the visit.
http://www.catacombes.paris.fr/en/catacombs/more-2000-years-history

Thanks for your help. We are planning to arrive at 9 a.m. (1 hour before opening). Still debating whether or not to purchase advance tickets. They are $27 (versus $12 + $5 for audio guide). Any thoughts?

If you plan on arriving an hour before opening, you probably won't need to waste money on advanced tickets. We were there three weeks ago. The first time we tried to go, we showed up between 9:30 and 9:45, and there was already a 2+ hour wait. We scratched that idea and came back a few days later, and arrived right at 9am. The kids and I held our spot, and my husband went out to find pastries and coffee. We didn't consider it a "wasted" hour because we also used it to eat breakfast, and we were able to get right in once it opened at 10am.

I too have been three times( which os twice too many, lol, but each extra time was because travelmates had never been and wanted me to take them)

We never took a tour or the audio guide. There are plaques that will tell you from which cementary the bones are from and the year moved into the catacombs. There are also a few exhibit in english. Never felt the need for a tour , its pretty self explanatory and you cant get lost.

Some tours claim to "jump the line" - but this is a pretty grey area.
Only a certain number of people are allowed down at one time - they must all exit and be accounted for, before anyone else can go in. So, either the whole group must wait, or it has to split up...??? It's never very clear, and I wouldn't buy this type of ticket.

Depending on what time of year you're visiting has a lot to do with it. Avoid weekends, get there early. If you have advance tickets, you still might have to wait to go in - it's more of a convenience than anything else.

Thanks everyone! We are planning to visit on a Thursday, first thing in the morning. Hopefully, it won't be too busy! I think we'll try it on our own.

PS - This is not exactly high on my to do list, so I'll let you know how it goes!

Just wanted to thank everyone who responded to my question and to report back on our visit to the catacombs on Tuesday, September 27.

The site is very easy to find. When we exited the metro at the Denfert-Rochereau station, there was a sign pointing across the street to the entrance.

We arrived at 9 a.m. (1 hour before opening) and there were about 12 people ahead of us. We were feeling pretty good about things until we noticed that 2 of the people were guides holding space in line for their tour members. Between 9:30 and 10 a.m. at least 40 people showed up with their coffee and squeezed in line ahead of us. We didn’t think that this was appropriate or fair.

By 10 a.m. the line stretched around the block. We estimated that there were at least 600 people waiting to get in. There was also a second (long) line that formed for people with pre-purchased tickets ($27 online).

Surprisingly, when the site opened at 10 a.m. both lines moved in an orderly manner. A person from the catacombs directed a few from the regular line, then a few from the pre-purchased line to enter. It took about 2 minutes for us to purchase tickets for $12 each. Based on our experience, it didn’t seem that there was much advantage to buying tickets in advance.

In order to enter the catacombs, you need to walk down 130 steep steps. Once inside you walk for quite a while (maybe a quarter mile) before you see any bones. The site itself was interesting but mildly disturbing due to the fact that you’re looking at the remains of people who have been disinterred.

Our visit took about 45 minutes. At the end, you need to climb up 83 steep, windy, wet stone steps. Be aware that you exit at a different place than where you entered. To get back to the entrance, turn right when exiting the site, then right again at the first main street (Avenue du Colonel Henri Rol-Tanguy). The entrance is about half mile down the street.

The catacombs would not be a place to visit if you have difficulty walking or with steps. I am a bit claustrophobic but it really didn’t bother me. I wasn’t thrilled about being underground for so long but the “hallways” were wide (4 feet) and the ceilings were pretty high (I’m short but I’d guess they were over 6 feet high). Also, since they limit the number of people entering the site, it wasn’t crowded. It is damp, cold, and dark in some places. Overall, a unique experience.

Thanks for all your help and guidance!

Nice of you to come back and report your experience! I also think a guide should not be able to save 40 freaking spots... !