What matters is not the length of time you're doing meditation, but getting into an Alpha brainwave or an Alpha state of consciousness (it is just below Beta, our normal alert consciousness, and is ideal for creativity and mental sight). If you want to get into deeper states of consciousness, you can look into guides for getting into Theta and Delta states.
There are two forms of scrying I've found common in all of the forms I've seen and they are psychic vision based and physical vision based. Using smoke for scrying is often a form of physical vision based scrying, while scrying into a black mirror will often provide a blank surface for psychic or mental vision to occur (it is my personal belief that our mental vision can be a form of conscious interpretation of psychic energy as we all have to interpret our physical senses before we actually 'sense' them).
Are you going for physical or psychic vision based scrying?
Time of day may or may not matter depending on your associations with time and what state your body and mind are in. Often, I find time of day may influence a reading, but it is not strict in my having to only read a certain time of day.
How long you do the reading is also up to you, but in general, just go as long as you feel comfortable with it.
Words also may or may not have influence on your reading depending solely on you. Do you have any mantras that aid you? Does your brain associate better in your native language or in another languge, or does it not matter? Do you like the energy the words bring? Think about why you would use words, what meanings are associated with the words, and say them as best you like.
Personally, I don't use any words because I'm not partial to using them in readings or workings unless I am using them for affirmation of calling or dismissing energy. What it boils down to is personal preference.