Poitiers is a city in France.
South towards Bordeaux
Take bus #4 in the direction Chantejeau Croutelle and get off at the stop Pte A Miteau (Centre Com). After getting off the bus, walk toward Ave Da 8 Mai 1945 and take a right on it. It will take you around 10 minutes or so to walk to the rotunda where you can stand to get rides either going down the A10 toward Bordeaux or the N10. Cars have to slow down at this Rotunda. You will see signs at this rotunda for the A10.
It might actually be helpful to walk to the paypoint. Instead of trying to get on the A10 on the right side of the paypoint you can also cross the street in front of the paypoint. Once crossed there is a small parking space with plenty of room to stop. Trucks leave here the A10 and take the N10 to go to Bordeaux/Spain. I guess they do so to save money. If you cross the street and wait for the trucks to come from the autoroute chances are high a nice trucker gives you a lift on the N10 to Bordeaux or even further south if so wanted; even more so since you can talk to the drivers that have a short break on the parking lot. (Don't let yourself be confused that you are now hitchiking in the direction where you came from!) Once i had figured that out i got a ride within 15mins whereas on the other side i had wasted 4 hours. On my arrival back in Poitiers 2 weeks later i found a guy at the roundabout who had already waited over 1 day!