When writing a song what are some things you do? i.e do you decide on a chord progression and arpeggiate it a certain way? Do you have chords and pick each one differently? I'm looking for some techniques, because I come from the school of 4 chords that are strummed in 8th notes and sang over.

And also what are some picking patterns you like? such as 5/2, 3, 4...etc list string order please.
Read about compas. Learn a few palos of flamenco well. You might be able to come close. There are no magic techniques for flamenco, only solid rhythm and knowledge of the palo you're playing in.