There's a moment on every hillwalk when the map stops being decoration and starts being the thing that gets you home. Perhaps the cloud has dropped onto the ridge, the path has vanished under a bog, or the light is going and the summit you wanted is still somewhere ahead. In that moment, the walkers who cope are not the ones with the most expensive kit. They are the ones who can read the paper in their hand.

None of these skills are difficult, but they do need practising somewhere safe before you rely on them in anger. Here are the essentials to get under your belt.

Know What Your Map Is Telling You

In the UK, the two mainstays for hillwalking are Ordnance Survey Explorer maps at 1:25,000 (4cm to 1km) and Landranger maps at 1:50,000 (2cm to 1km). Explorer sheets show field boundaries, walls, streams and paths in far more detail, which makes them the better choice for tricky navigation in poor visibility. Landrangers cover more ground and suit long ridges and big mountain days.

Check the date and edition. Fences get removed, forestry is felled, and new tracks appear. An old map is not useless, but treat anything doubtful with suspicion.

Learn the legend properly. It is worth half an hour on the kitchen table. Pay particular attention to:

• Right of way markings and public footpaths, bridleways and byways
• Contour lines and the spot heights printed along them
• Water features, including springs and marshy ground
• Access land boundaries and forestry
• Cliff symbols, crags and scree

Fold your map so the relevant section is on top, and keep it in a clear case. A map buried at the bottom of a rucksack may as well be at home.

Grid References: The Language of Location

A grid reference pins down a point to within 100 metres, which is precise enough for almost any hill situation. Every map has numbered vertical lines (eastings) and horizontal lines (northings).

The golden rule is along the corridor, then up the stairs. Read the easting first, then the northing. Getting this the wrong way round is the single most common beginner's error, and it can put you a kilometre out.

For a six-figure reference, take the two-digit easting, then the two-digit northing, then estimate tenths of a square within that kilometre. So a point three-tenths across and seven-tenths up inside square 34 / 56 becomes 343 567.

Practise at home with a known location, such as a trig pillar near your house, and check your answer against the map. Once you can do it in ten seconds, you can hand a reference to mountain rescue if things ever go wrong.

Contours: Reading the Shape of the Land

Contours are lines joining points of equal height. On a 1:25,000 Explorer map they are usually 5 or 10 metres apart, and on a Landranger 10 metres. The closer they are, the steeper the ground. That is the whole idea.

Before you set off, spend five minutes simply looking at the contour pattern along your route and asking yourself what it means:

• Closely packed contours mean a steep pull or a dangerous drop, depending on which way you are facing
• Widely spaced contours mean gentle, rolling ground
• Contours that form a V pointing uphill follow a stream or valley
• Contours that form a V pointing downhill indicate a spur or ridge
• Concentric rings that shrink upwards with a spot height in the middle are a summit

Hafnells, crags and cornices all have their own contour signatures, and learning to spot them will keep you off ground you don't want to be on. On a misty day, the contours on paper are your eyes.

Compass Bearings and Navigation in Poor Visibility

A compass does two jobs: it tells you which way you are facing, and it lets you follow a bearing to a point you cannot see. The technique is straightforward but must be rehearsed.

To take a bearing from the map, lay the compass edge along the line you want to walk, with the direction-of-travel arrow pointing towards your destination. Rotate the bezel until the orienting lines line up with the map's grid lines and the orienting arrow points to the top of the map. Read the number at the index line. That is your grid bearing.

Now you must correct for magnetic variation, because magnetic north is not grid north. In the UK the difference is currently a few degrees west, and it changes each year. The information is printed in the map margin. Add or subtract as indicated to get a magnetic bearing.

On the ground, hold the compass flat and turn yourself until the red end of the needle sits inside the orienting arrow. The direction-of-travel arrow now points along your route. Pick a feature ahead, walk to it, and repeat.

A few habits will serve you well:

• Set the map to the ground using the compass before every leg
• Use handrails, such as walls, streams or ridgelines, to keep you honest
• Measure distance by timing and pacing, not guesswork
• Walk on a bearing in short legs with clear aims, not one long hopeful line
• Stop and relocate the moment you are unsure, rather than pressing on

Practice these skills on a familiar hill in good weather. Do a bearing leg you already know, then check how close you got. Do it again in mist. By the time you really need them, they will be second nature, and the hills will feel considerably friendlier for it.