Types of Map
You will usually get a photocopied colour map with your ride
pack. You are strongly advised to go out and buy anOS
map of the area, either Landranger (1:50000 scale),
or Pathfinder or Explorer 1:25000 (more detailed). The ride details you receive
will usually tell you which Landranger map(s) covers
the ride route. Pathfinder maps are currently being updated to Explorer, which
are the same scale but cover larger areas, and may be double sided.
Contour lines

Every 10 metres on 1:50000 maps and 5 metres on 1:25000.
Learn to recognise the shape of hills - is it a steep slope (lines close
together), or shallow one (lines far apart), is it a round hill with an obvious
summit or a plateau. Don't forget hills restrict your sight - you can't see a
church on the far side of a hill!
The picture shows
the contour lines for two hills and how the hills appear viewed from x.
Symbols
All maps have a key down one side - make sure you know what
all the symbols stand for. Some of the most useful are: 
churches - with a tower (top), spire (middle). Churches
without either (bottom)can be harder to spot, as they
can just look like normal buildings.
pylons (1:50000 top, 1:25000 bottom) are a great way to
navigate. They are easy to see from a distance and run in straight lines so you
can get some idea of direction.

rights
of way (red 1:50000, green 1:25000) should be signposted on the ground, so look
out for them, particularly when you are on the road.
Forests can be very hard to map read through. In
plantations, forestry tracks tend to move, so don't expect them all to be
marked on the map, or all the ones on the map to exist. Look out for any
streams, lakes or houses you may pass or any pylons you can see.
Schools are usually marked as Sch,
and in rural areas telephones and pubs (PH) may also be marked. Single farms
often have their names on the maps - a good way to pinpoint your location
exactly.
When on a road, is it straight, or does it have any sharp
bends on, to the left or right, are there any junctions you have to cross?