If you have pots on your balcony or terrace, huddle them together. Doing this helps create a humid micro-environment, allowing the plants to retain moisture and get some relief from the heat.
Also, use clay pots instead of ceramic ones in the summer. Add a light, natural fertiliser every 15-20 days. And make sure you pluck off any yellow or wilted leaves immediately, otherwise they'll spoil the healthy ones too.