Ross Campbell's classic 1977 book, How to Really Love Your Child, examines how to show preteen children (he has another book about teens) that we love them in a way they understand. After quoting 1 John 3:18, Dr. Campbell says, "The purpose of this book is to examine how parents can put their feelings of love into action. Only in this way can they convey their love to their child so that he will feel loved, completely accepted, and respected, and able to love and respect himself. Only then will parents be able to help their children to love others unconditionally, especially their future spouses and children" (page 35).
Three keys he gives are:
Eye contact."As early as two months, [a baby's] eyes lock on another set of eyes. Already he is feeding emotionally, and even at this very early age his emotional tank needs to be filled" (page 44).
Physical contact. "It seems that the most obvious way of conveying our love to a child is by physical contact. Surprisingly, studies show that most parents touch their children only when necessity demands it" (page 45).
Focused attention.This is "giving a child our full, undivided attention in such a way that he feels without doubt that he is completely loved...[It] is the most demanding need a child has, because we parents have extreme difficulty in recognizing it, much less fulfilling it" (page 56).