Pilchards, tuna, dolphin fish, squid, sargent baker and small octopus make good snapper baits as do yellowtail and slimy mackerel. Fresh mullet strips are my all time favourite bait for snapper and for that matter most other offshore species. Frozen mullet is also good, as long as it is not suffering from freezer burn. Summary I don't consider there is a best time of year to target big snapper as there are too many variables to consider. Big seas can bring them in close and on the bite because of the large amount of food that is dislodged.
Floods can also throw a spanner in the works as they also move a lot of food.
I've kept a fishing diary for the last seven years, yet I still can not put my finger on what is prime big snapper time. Most of my fishing is on the NSW north coast where over the years big reds have been landed during every month. The situation is perhaps different where you fish. Early morning, late afternoon and into the night are the best time of day to target them. But again, we have landed big snapper during the middle of the day so really the more hours you put in the better your chances are.