How to read Crochet Chart or Graphed Patterns
The easy way for the beginner to the most advanced. 
When you come across a crochet pattern with a wonderful design.   You often wonder how they got it on there like that and with such precision and accuracy.   Will let me tell you, it was probably done with a graphed chart of some sort.   This process is also known as or commonly known as Filet crochet

This is a wonderful way to make beautiful designed afghans and throws or whatever your imagination can create with a graph chart design.    Typically the filet crochet is done using the double crochet stitch.  I got to honestly tell you.   It takes a lot of patience to do this type of crochet.   I am sure for the well advanced crocheter.  This type of crochet is easy and quick to them coming strictly by nature.   Now to the beginner or intermediate crocheter this type of crochet is a bit on the tedious side.   Lots and lots of counting.   If you don’t keep count you’ll lose your place.    I have found an easy way to follow a graph chart.  
Follow it sort of like this:

Say you have for example:
10 squares on your graph paper. 

Creating your foundation chain.  
* 1st square count as 4 chains
* every square after count as 3    
* Add enough chains after the last
  to turn and create the next row

You will have a total of 31 stitches plus 5 more = 36 chain stitches.                              Turn your work. 
You will do a double crochet in the 9th chain from your hook that will be your 1st double for that row. 
                        That is basically it.  

You can search in the links in the learning center for more helpful advice on filet crochet.   This is just a general idea of how it is started.   However,  to read the pattern I have here or any graphed chart ; which is what I am writing about.     How to follow the chart once you have mastered the filet crochet stitch.  

Note:   You can also shrink the size of the pattern by using only 2 double crochets for each square or three.   I don’t however recommend using one stitch per square.   It tends to distort the image.   Sometimes even using a smaller hook will reduce the size as well.

After you have established your first row, which I also recommend doing this in one color its just easy for the first row. 

*Get a post it note and a pencil.*

You will use the post -it note to keep you on the right line moving it upwards as a guide so to speak.  

Figure out what side you want to start at.   Generally it is best to start at box 1, and then working your way across to the end of chart.  
Turn your work.  

Now when going back follow the graph from box 10 to box 1 of the next row,  just going backwards.    Then follow it in that pattern all the way to the last row.   After every row you complete take your pencil and mark off the row.  (incase the post-it falls off the paper)

This was just my way of doing it, not that it is the right way.   Everyone has their own way of doing things.  
Hope it was helpful. 
                                Have a wonderful day.