If your negotiating position isn’t great but you see the other side is worried about losing the deal, you can’t go wrong by coming on strong and playing to the other side’s fears.
by这里表示以什么方法的方法状语，coming和playing怎么样理解这两个动名词的意思？
come on strong给人以强烈印象。play to the other side's fears可理解为针对他们的担心发起攻击。题主的问题可理解为：你表现出态度坚决并且借助他们的担心来提条件，如此你绝不会出错的。