"volitional + to omou" = "to intend to do such and such", "to think of doing such and such"
When talking about a third person, use "to omotte imasu."
Konban wa kusuri wo nonde hayaku neyou to omoimasu.
I think I will take some medicine and go to bed early tonight.
Ane wa arubaito wo sagasou to omotte imasu.
My older sister is thinking of looking for a part-time job.
Schaum's Outline: Japanese Grammar