The best gift I was given for my crochet was a counter. This allows me to know how many rows I have completed as I go along. After about 20 – 25 rows, I recount, place a marker and update my counter if needed. If you are single crocheting each row, recount the end stitch to find correct number.
Some patterns require counting as you go along, For example, ZIGZAG pattern requires same amount of stitches up and down the sides of points to ensure even pattern. PERFECT CIRCLE requires counting to make sure only 6 stitches are added in each row.
If your edge is unintentionally crooked, it is because you missed a stitch or added a stitch. You may not notice until a few rows later, so you can either move on, making sure the next row has the correct number of stitches, or do like I do, pull it all out and fix the error.