General Synonyms:
* Prescribe
* Stipulate
* Specify
* Enjoin
* Order
* Command
* Demand
* Impose
* Declare
* Pronounce
More Specific Synonyms:
* Dictate (to a machine): Transcribe
* Dictate (with authority): Rule
* Dictate (with force): Force
* Dictate (with control): Control
The best synonym for "dictate" will depend on the specific context of your writing.