Wait to cast Void Swarm until there are nearby enemies for the Voidling to attack or kill.
Use Call of the Void and Nether Grasp to renew the duration of Malefic Visions on enemies.
Avoiding damage in lane maximizes the uptime on Void Shift, increasing Malzahar's safety dramatically.
When Malzahar hits a spell on enemies affected by Malefic Visions, the Visions are refreshed.
Avoid minion waves that have been affected by Malefic Visions. You never know when they may die and pass the Visions onto you.
Malzahar is especially dangerous when he has built up his Void Swarm.