A map is a graphical representation of the ground. Your brain needs to provide a link between what's on the paper, and what's on the ground. This is called terrain association. Let's break down the type of useful information we get from maps.
Point features are those that are clearly discernible from the surrounding environment. Mountain peaks and crags are obvious examples. Less intuitive are junctions such as ridge or creek junctions. Be circumspect when using creek junctions. They are often indistinct, so it is not always obvious where the junction is, and they could change over time. In addition, there are generally multiple junctions along ridge and creek lines. It is possible to confuse which one you you are seeing in front of you, with which one you think is on the map. Resist the temptation to 'fit' the map into what you think it should be.
Man-made features such as quarries, reservoirs, bridges, culverts, trig stations, pylons, and Microwave repeaters, and buildings are also useful. Study the map legend! Be aware that manmade features can get removed, constructed, and it is possible, although less likely nowadays, that features such as powerlines might represent the position they were intended to be constructed, not where they ended up.
Some point features can be difficult to discern from the landscape. On the maps these are spot heights - points with an elevation, but not readily discernible as they are within a contour height of the surroundings. They are usually obvious on the ground, but hard to pick at a distance.
In short, point features are the most easily recognised and hence any bearings to and from them are more precise. Indistinct point features such as junctions and spot heights may be a bit more 'fuzzy', and bearings will be less precise.
Linear features include natural features such as cliff or steep slope faces, ridgelines, and rivers. Many man made or modified features fall into this category. For example fencelines, powerlines, vegetation breaks, roads. While linear features don't provide a point to take a bearing to (except maybe at their end point), they are very useful for orienting your position and track on the map.
Often there aren't any convenient single, easily identifiable features on a map. Rather, the shape of the terrain must be deciphered from the map. This is where you have to visualise what the contour lines on the map translate to on the ground in front of you.
Hills are characterised by concentric contour lines increasing in altitude - kind of like a multi-ringed donut. Mmmmm. donuts! At the center of the donut is the top of the hill. If it is prominent enough it will be denoted by a spot height.
Depressions are hills in reverse. As with hills, they are characterised by concentric contour lines, however the lines decrease in altitude. In this example, I've chosen a particularly large depression - occupied by a lake... The main point to keep in mind is to look at the altitude values just to double check you are looking at a depression and not a hill. If, as in this case there is a lake there - it's a bit of a no-brainer. Thank you Newton for inventing gravity.
Any increase or decrease of altitude with horizontal distance constitutes a slope. To the intrepid hiker, this means you are either walking up or downhill. Contour lines that are close together indicate a steeper slope. Slopes are often described by their gradient - the change in height divided by the map horizontal distance walked. For example, if you measure the distance between two points as 300m, and the difference in the contour lines is 100m, then you are looking at a 100:300 or to simplify 1:3 gradient. This is important to know when planning your route - steep slopes are harder to climb. It is also a useful skill to help identify your position. Knowing the slope, and direction of the slope is one of the topography features used to place yourself on a map.
Slopes have different shapes. Even slopes are characterised by contour lines that (unsurprisingly) are evenly separated. Basically like walking up a ramp. Small spaced, progressively widening contour lines indicate a convex slope. In other words, it will be steep initially then progressively flatten out leading to that Phew - I'm nearly there feeling. In contrast a concave slope will start with widely spaced lines, and close lines to the end. In other words, you will trudge along relatively comfortably until you hit the 'Bloody hell! Do I really have to climb that?' moment.
Ridges are elongated raised areas at the same altitude - ie. you just walk along them at the same height. Often with steep sloping sides. Ridges are often good lines to travel on. Aside from being obvious features to follow, vegetation is usually less dense on a ridge line as they are more exposed to wind and erosion.
Spurs can be thought of as ridge lines that decrease/increase in altitude. The contour lines are U to V-shaped, with the pointy end at the low part of the ground and the open part at the high part.
Where you have a spur, you generally have a Re-entrant (apparently called 'draws' by our 'Merican brethren) next to it. Reentrants are small valleys. The contour lines are U to V-shaped when pointing toward the high ground - ie the pointy end of the V is toward the high ground, and the open and at the low ground end. Valleys are just steep re-entrants. It's not a hard and fast distinction, just a matter of degree. The example in the diagram could be thought of as a small valley, depending on your head for heights I suppose.
Cliffs or escarpments are, well, things not to blithely walk off unless you want to lose altitude very quickly. Joking aside, if you intend to navigate at night be incredibly aware of the possibility of walking off one of these things. Aside from the contour lines being incredibly close together, many topographic maps will have a characteristic hatching pattern depicting cliffs.
Saddles are the low bits in between two hills. On the map they have an hourglass shape. In profile they are kind of like a double scoop icecream.
Basic skill exercises
Here's some homework for you. The most fundamental, and I think rewarding, skill in navigating is to be able to mentally orientate yourself to features of the landscape around you. In these urban-centered times, it is too easy to become divorced from your surroundings, where directions take the form of “Take the XX Highway until you reach the YY Turnoff, stay in the left lane until the 3rd off-ramp...” and so on. Or in the case of some directions I've received “… then when you reach the McDonalds, you've gone too far. Turn around and go right at the Ikea. Stop when you reach the policeman.” “But surely the policeman will no longer be there?” I replied. “Yes he will. I parked my car on his foot..."
To help develop basic skills, get a map, a compass, plonk yourself in a known and preferably elevated place and observe (this being the key word).
From your current position, without looking at the map, sketch a diagram of the landscape around you. First, where are you? Are you on a hilltop, a hillside. Is there anything close by that is obvious like a creekline, road, bridge. Observe and draw the obvious features relative to your position. These can be hilltops (spot heights), intersecting ridges, man-made features such as towers and trig points. How far away from you are they?
If a map is a 2-dimensional representation of the ground, this picture has to be retained in your head. What better way to get something into your head than to force yourself to draw it? As anyone who has done anatomical drawings in biology knows, drawing forces you to observe things. Similarly, any soldier who has trained in reconnaissance or sniping knows how to generate field sketches for exactly the same reason. Even a basic soldier will be familiar with a mud-map (a rough model) of terrain in which they'll be operating to get a mental picture of the ground without having a map. If none of these apply to you, consider how useful it would be if you were hiking on a trail in which only the most rudimentary of instructions were given. Wouldn't you like to have your own sketch of the terrain in case the instructions were less-than-perfect and you missed a track junction or wandered off the track altogether? This exercise forces you to study the map, not just skip over the pretty bits.
Now the moment of truth – how close to the real map was your sketch? Orientate the map to north-south, look around and see what you observed and drew, and what you missed. How good were your distance estimates? Use your compass romer, a ruler, or even a scrap of paper to measure distances off the map scale. I can't stress how important this is to master – you need to know in the ballpark how far away things are. With practise you will find different conditions alter your estimates. When the sun is behind you, objects will be brighter and appear closer and bigger. When the sun is in front of you the reverse is true. Objects that are above you appear closer than objects below you. By measuring from the map the true distance, you will develop a feel for these effects.