Practice makes perfect
Even if it doesn't make you perfect it will make you better! You cannot hope to improve your grid reference (GR) skills by reading about them. So get some practice!

4 figures good: 6 figures better
A 4-figure grid reference is useful for showing an area but it shows the whole of a grid square. There are 100 6-figure references in each square, so a 6-figure reference is 100 times more accurate. You will get more marks for using a 6-figure reference to refer to a point within a square.

Imagine the sign post
A figure reference refers to two lines. They cross in the south-west corner of the square.

A 6-figure reference also refers to the two lines that cross in the south-west corner of the square, and then you have to count off tenths.

Start in the south-west corner, then count tenths going east.

Start there again, and count tenths going north.

The diagram below shows the starting point for giving references.

Counting eastings is just like reading English

Always count eastings from left to right.

'0' is still a figure
When you are counting tenths, '0' should not be ignored.

In the example below, the 6-figure reference for the lake is 010990.

Why not just give a 4-figure reference - 0199? Why not start at the south-west corner and count across ten tenths to give 000 then up ten tenths to give 980, giving a 6-figure reference of 000980?

Gaps and dots may help you to learn, but this is not the proper way to read maps
If you were asked to give a grid reference for the Majedski Stadium in Reading you should think about it in this way:

SW corner, easting is 70
Stadium is 8 tenths across the square
. so that is 70.8
SW corner, northing is 70
(Check: are they both 70? - yes!)
Stadium is 3 tenths up the square
. so that is 70.3
Put them together, easting first (E comes before N in the alphabet) to give 70.8 70.3
But proper map readers write this as 708703

Do the 'belt and braces' check
People who want to be sure that their trousers don't fall down wear a belt and braces. People who want to be sure that they have got their GRs right always check them back to the map. When you have worked out a GR go back and check it by finding the reference on the map, using the grid lines.

Don't overdo it !
Examiners like you to use a GR or two in your answer when it is relevant. However, There is no need to give a whole page of them! Once you have shown that you can do GRs, and have given examples in the relevant place, you will not gain extra marks for giving more of them. Two GRs in one answer is usually enough.