Start with the obvious stuff that covers 80% of summer-related issues:

• Keep it out of direct sun. That means no dashboard, no windowsill, no back pocket while you sit outside. A bag or shaded pocket works fine.
• Store it upright. When a vape lies on its side, the liquid can sit against the mouthpiece and seep out. Standing it up prevents that.
• Don't leave it in a hot car. Even for 15 minutes. The temperature spike can mess with the battery and the coil.

If you only follow these three, you'll avoid most leaks and battery hiccups. The rest is fine-tuning.