Strategy usually requires some sort of planning. You'd probably use strategy when faced with a new situation or a plan of action designed to achieve an overall aim ie. the strategy to learn english within a fixed time period.
Technique is a procedure or skill for completing a specific task. I'd imagine this would be used for predictable events, ie. technique for solve to remove your indonesian accent from American english.
Method is a way something is done. Perhaps used for routine tasks.