If it is a breakthrough trading strategy, you should choose the entry point when you break through the corresponding resistance level or fall below the corresponding support level.
Because it is a breakthrough, the position of the entry point is often higher than the resistance level or at the support level.
If it is a shock strategy, it is just the opposite of a breakthrough strategy, shorting near the resistance level and doing more near the support level.
Because it is a shock, the default is not to break through, then the opening unit is often equal to or lower than the resistance level and equal to or higher than the support level.
There are other strategies for trading according to indicators or patterns, and the entry point is also determined according to the entry position defined by the strategy.