A Forex trading plan is not very different from any other plan. It is an overview of your planned trading activity based on certain parameters you have chosen. It is akin to a to-do list that needs to be accomplished in trading activities.
The main idea of the trading plan is to develop a set of rules to follow and to know how to implement them. Once you have these rules written down, it becomes easier to apply them, as there is a clear action plan for how to manage daily trading.