We spent a week in Arles, France and found a recommendation for Imagine Tours in Rick Steves' Provence tour guide. We had a day tour to Nimes, Les Baux-de-Provence, and Pont du Gard and had a delightful time with our tour guide, Richard. He was a friend for the day as well as a guide. Our actual tour was on a Thursday but Richard met us for coffee in Avignon on the preceding Tuesday to discuss our interests so he could better plan our time with him. After coffee, he showed us around Avignon for a little while and gave us some suggestions regarding where to eat.
It is interesting how Imagine Tours works. The tour guide is a volunteer...tour fees are paid to Association Imagine Tours (a "not-for-profit cultural association"). Of course, a tour guide tip is always appreciated. Half-day, 3/4 day, or full-day excursions are available. The association fees may be paid in euros to the volunteer (which is what we did) or via PayPal. Credit cards are not accepted.
Since the guides are volunteers, it's necessary to schedule ahead to ensure availability. It was, however, easy to schedule the basic tour through their website and via email. We provided the places we wanted to visit and our available dates. The association found a volunteer who was available on a date we had available. As mentioned above, Richard also met with us in person prior to the tour day to refine the tour based on our interests (e.g. we're more interested in seeing antiquities than shopping).