To add to EoS posting, don't use those marked CB or telecart. The "man" may not be green, but may be white and appears to have a flat peaked cap although I have never ever seen a toll-collecter so attired.
At off peak times there may not be many booths open, so first look is for a green downwards arrow rahter than a red X above the lane.
Payment lanes tend to be to the right hand side (their nearside) as you approach.
Beware that some exit booths are now unmanned and you have to use either coins or card into appropriate slots. With a card you can normally choose to get a recepit (recu) and you don't need to enter your PIN.