Bryan,
Any of the booths, except for those where you pay with an electronic tag - usually labelled "Telepeage" - and you may want to avoid the unmanned "Credit Card only" booths until you are a bit more familiar with the payment systems.
As a generalisation, there are two types of toll points - those where 6 or more toll booths are strung across the autoroute with electronic signs above each booth.
Go for the booths with the (green?) symbol of a booth operator (manned toll booth) and pay with a credit card or Euro. The Telepeage toll booths have a large (purple?) T symbol. The unmanned credit card only booths have a credit card as the symbol.
The other type of pay point is where you leave the autoroute at a minor exit and this time there is only one toll booth, usually manned 24 hours.
Robert
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