Each box on the brevet needs filling, either with a stamp or, if an info control with a manuscript 'answer' to the question printed on the brevet. The routesheet will specify the existence of each info control with (good practice) clarity over its precise location. But the question will not be given thereon.
When you go through the route this week (on RwGPS say with
http://www.bikehike.co.uk/mapview.php open too for the OS mapping) try to identify the place and GoogleSV it to help you recognise when there. Since you won't yet know the question, you can't pre-determine the answer.
When you pick up your brevet at the start, look for the info control questions and memorise them (there can't be more than one in a well planned 100km imho).
Arriving at the spot discern the answer to the Q and either write it in the box or memorise it for later. Some riders take a photo of the feature to refer to at the next cafe stop: younger ones can do this without stopping (eg price of petrol at x garage). Quite likely there will be riders faffing around at the info control site. If the slightest doubt, when next riding in company, ask them whether the answer you have is the same as theirs.
The quality of info control questions reflects the personality of the organiser.