Making the sole involves a lot of counting. What you have to keep in mind is that the sole in most cases is made of two identical halves, one left half, and one right half. So whatever increases you make will be symmetrical on both sides. If you’re counting goes wrong then your sole will look like it is turning to one side or has an extra bulge on one side. So make sure to count your stitches after each round.
For beginners, increases mean doing more than one half double crochet or single crochet etc. into the same stitch. There are cases where the pattern requires the sole to have a sharper curve on one of the sides, but that is rarely required for baby booties. Each round in the sole is made using a mix of half double crochet, single crochet etc. This is to make the sole wider at toe side and narrower at the ankle side by making the longer stitches on the toe side alone. So watch out for the changes in the stitches in each round, do not end up doing sc where your pattern calls for hdc or vice versa. I hope these tips help you in clearing some of the confusion involved in making baby booties.
4. Again, last but not the least when the pattern gives different sizes, circle all the variations for the size you choose before starting to work on it. All the best with your baby booties!