Because this is a topic that comes up fairly regularly, I’ve posted my thoughts on developing trading plans here, in case anyone finds that useful.
Edit:
And while I’ve not read the book that @LaughingCharlie recommends, I do support the general sentiment. Once you find a general strategy or set of indicators that work for you, start digging deeply into the material on that topic written by the top traders. For me, John Bollinger’s book on Bollinger Bands was one of the turning points in my ‘career’ as a trader. Forex trading is a game of inches, and the step from ‘cursory knowledge’ to ‘deeper understanding’ is often enough to put you into the black.