Parameters go on the left of the colon and the dialogue text goes on the right. You can omit any parameter and specify them in any order. Parameters are separated by spaces. If you need to use a name which contains spaces, wrap it in quotation marks e.g. "John Watson". Parameters are case insensitive. Blank lines and comment lines starting with -- are ignored. A line of dialogue text on its own will be spoken by the most recent character. You can omit dialogue text, but remember you still need to add the : character at the end of the line.
You can use the normal string subsitution syntax {$VarName} anywhere in the conversation text. For example if you have a string Flowchart variable called PlayerName you can embed this in a conversation like this: