(Note: this sample is intentionally large to be easier to explain the idea.)
When you follow the instructions for a crochet project, it is common to find a reference to the number of sample points and careers by CC-crafted with a needle and wire thickness specified, as well as the type of crochet point to run.
So, before you start working your piece, take a sample with little more than 10 by 10 cm (it is always better to have a few centimeters to it easier and accurate measure what is intended) and without requiring great care. Then, extend your sample on a flat surface and check the measures indicated by the standard or scheme that intends to do.
From this specimen can conclude whether it is necessary to make some adjustment: If there are more points between the pins, you have to work with a thicker needle; If, on the contrary, there are not enough points between the pins, you have to work with a thinner needle.
In addition to the foregoing, the crochet sample may have another utility: If you want to make a particular piece but can't imagine the length as this will be after, can do the same aforementioned sample and, from it, make a very simple calculation to find out how many points and careers will have to work to get the length you want (e.g. : If in 10x10cm 12 points and 5 are included, to make a small blanket of 100x100cm have to do 120 points and 50 careers).
This means that, with the needle and thread and with point and pattern that you chose, with a small sample of crochet can learn how many points and careers need work to make the piece you want, and with the measures that you want it.