It is important to test the crochet strength to ensure that your finished product is the right size.
When testing crochet strength, it is best to make a sample that is a few cm higher and wider than stated, so that you can measure in the middle of the sample rather than from edge to edge, because the sides may give slightly different measurements.
You should always follow the crochet tension stated in the pattern and not the one stated on the yarn.
There are probably more good tips.