Professional trader know the methodology of trading. Most skillful trader didn't trade with emotion they have their predetermined exist plan and have good trading plans.
There is no specific methodology while trading. the only basic method is buy low and sell high and it is the basic thing to remember and understand the market and monitor it carefully and understand the resistance level and make a stop loss for damage control if something negative happens .
But I believe each and every trader will be doing same buy low and sell high still there are many different strategies and management techniques need to be applied to have a better trading experience.
A professional trader will find easily where to buy and where to sell whereas a novice trader will be struggling to find out those buying and selling points. Precisely the technical part may differentiate professional traders from others.
It all boils down to knowledge and experience since amateur trader does not have any will probably make a lot of mistakes but the experimented trader will have both and will be able to make money even in a difficult market while the amateur will have problems making money even in the best of circumstances.