Ensure all the little things you will need such as knives, gaff, bait, extra tackle etc can be seen and are within easy reach. Use a deep water berley system, such as The Secret Weapon, to get a heap of berley down to the bottom before it gets dark. Because fish caught tend to be bigger at night it would pay to step up a line class. This puts you more in control of the fight and will save time in getting the fish to the boat. In fact before you gaff any fish aboard, check out what it is.
Bronze whalers look a lot like big flathead and jew in the dark.
When you return to base, however late that might be, remember to wash down all the gear and hose off the boat and trailer. That ever present enemy, corrosion, waits for no man. If you want to flush the motor, please respect your neighbours. If it is too late, leave it to the morning. It's a good feeling to fish into dusk.