A reference sheet on reading the metric scale.

Below is an example of a metric scale.  This particular one measures length (mm)  

If you count between the 0 and the 10 on the scale above, you will find 10 sub-divisions.  Each is worth 1mm.  This scale is accurate to 1 decimal point, and you need to estimate the relative position between two subdivisions.  A hair to the left of the "10" on the scale above is 9.8mm.

You might also see a scale it like this, usually on a balance, displaying grams

On this scale, each sub-division is worth .1g.  The larger division between "0" and "1" is .5g.  If the pointer on the scale was exactly in the middle between the .5g sub-division and the .6 sub-division, the value would be .55g.  This scale is accurate to 2 decimal places.

The same rules apply to read a balance (g) or a graduated cylinder (ml) or a meter stick (mm).

It is very important to note the units the scale is using.  The top scale is using mm, the bottom is using g.