Should I be thinking about parenting skills when my baby is fifteen to eighteen months old?

No, much earlier ! Parenting skills and style need to be thought out and formulated before the birth of the child because parenting skills help to shape the child's personality from the start. For ex., parenting skills include calmness, consistency in expectation, communication, follow through, rewarding, & loving correction--skills which help develop confident, well balanced children with a strong skill sets.
Yes. As your baby begins to walk and seems to understand the word "no, " it is easy to expect too much from them. The main job for a parent is to teach. Teach the child what you want them to do. The early toddler years are marked by confusion and an uneasy blend of dependency and emerging independence. Temper tantrums often increase at this age.