I have to be honest and say I haven't read a lot of books on the matter, but I have read a lot about childhood development in University, studying to be a teacher, and I have read a lot about Non-violent communcation as an educator for peace and conflict resolution, and that has all colored my parenting choices to one degree or another. I am also fairly driven to avoid conflict and violence, and to look for solutions in my life, so that too has helped.
My best resource for help has been here and in particulr a huge shout out to Mamazee who always has stellar advice and a gentle perspective on parenting issues.
My best tools have been modelling, and empathy. It has also helped hugely to remember not to take the tantrums and the bad behavior as a personal reflection of my child's feelings for me. It is hard to remember.
I recall reading once in Happiest Toddler on the Block that toddlers are very much like foreigners in a strange land trying to speak the local language, thinking they are doing and okay job and not getting anywhere. As a traveller I found that analogy to be one of the best reminders for me of what my toddler and even my older child is going through. I know what it is like to be searching my internal ohrase book for the words and not quite finding them, or thinking I have found them and not have people understand me...not a big deal when I can see and reach and meet my needs myself, a HUGE deal when I am tired, hungry, in pain, or afraid. At the age of 35 I still ocassionally have temper tantrums of a sort, definitely melt downs, when this happens to me, and I am now at about the fluency of the average 10 year old spanish speaker. So when my kids are mid-melt down, or are waging an attack of bad behavior, I ask myself first...what's going on? Does he need a snack? Does he need a nap? Does he need a chat and a cuddle? What's the dilly-yo? Then I feel in a much better place for problem solving, because rather than feel attacked, I feel there is something I can do. Feeling impotent against a child's tantrums is terrifying, and it makes me irrationally angry about the tantrum. Understanding that these choices are normal emotional reactions for someone who doesn't have the language (or maturity) to express their feelings or needs, helps a lot.