Yesterday’s news reported that the best days to book a flight are mid-week. They also recommend calling after midnight on Tuesdays, and state that 45 to 50 days prior to your planned trip is the right time-frame to get the best rates.
When it comes to lodging, you can plan flight and hotel on a travel site and they will claim to have saved you a bit, but you can frequently get extra discounts on your own, by becoming a rewards member of one chain. This works especially well when you frequently visit the same city, as when visiting grandchildren. I have also found that, when you deal directly with the hotel, the rooms available are in better locations with better views.