S.G.
Phone calls between you and him-time, date and what was said if there was time agreed to for him to pick her up, disagreement on time or day, if you or he needed to change a time or a day, etc.
When he comes in contact with her-picks her up/drops her off (date and time) and was he on time or late (how late), where the pick up/drop off happened (your home, his home, McDonalds), what condition she was in at drop off (clothes clean, hair neat, dirty or clean face & hands, any cuts, busies or scrapes and how bad).
If he doesn't show up for a visitation with her, cancels a visitation, takes her somewhere inappropriate, does something that could endanger her, he tries to argue/fight with you in front of her, takes her clothes shopping, to the park, to a B-day party, etc.
You have to write down the good and the bad because if you do end up in court, you'll look like the bigger person because you didn't just keep track of the bad things!
Good luck
S.