The biggest challenge when making Granny squares are that they often do not turn out to be the perfect squares with the crisp edges. This creates difficulty when trying to join two squares together.
So some tips -
When making a Granny Square:
1. Choose the correct size hook for the yarn you choose.
2. Hold the loose end of the yarn with even tension throughout the process. If you keep varying the tension, the size of the stitches also vary, which creates uneven squares.
3. When using more than one type of (or colour) yarn to make a square, make sure that the yarns are of the same ply and thickness. Else, the square can become uneven.
When joining Granny Squares, if the edges of are curved up like this, it is difficult to get the stitches correctly.
Here is one tip. Hold the squares to be joined together. Insert a smooth thin rod through the holes in the edge and hold it taut till you get a neat corner on the square. I used my crochet hook itself to hold the stitches up.
Now you can see that perfect bend at the corner as well as identify the stitches easily.
Happy joining :-)