My club currently runs a set ride on Saturdays - always leaves from the same place and always follows the same route. we have a 30 mile and 20 mile option.
The 30 mile tends to be "the Saturday morning world championships" with 25-30mph pacelines. The 20 can be a little fast for some begginers. a lopt folk only want to ride an hour and half, and get mad at the regroups for slower riders.(there's two at the summit of the "big" hills) I've thought about coming up with a slower pace, but I'm taking a break from that right now.
The ride starts at a Coffee shop in a shopping center. There's usaully a lot of socializing Aprez-ride, which folks seem to enjoy.
I think being welcoming and encouraging are the key. Finding folks will to sweep is the key.
I personally like a variety of terrain and secenery. I'll usally do the 20 just to chat , and then do some more on my own,since I seem to be the only one who'd rather do a distance ride on a Saturday vs a Sunday.