During the laning phase you want to apply constant pressure to your laner by killing your minions as quick as possible. If your lane shoves under tower it becomes hard for your laner to kill lane minions.

Pay close attention to the enemy jungler as Singed can be weak to fast ganking junglers. If you're against a slower ganking jungle / power farmer such as Nocturne, take ghost instead of flash as you wont need the escape potential in the early game.

During the mid game you want to be roaming and looking for kills whenever your laner isn't shoving.