By default, new Tinderbox documents are set to update all agents automatically. In the vast majority of cases this is what the user wants. All agents run all the time, unless they have had their $AgentPriority altered via the agent's Rename dialog or directly in action code.
In addition, you can trigger an immediate 'Update now' from the File menu. This runs all agents once, regardless of $AgentPriority except for any agents expressly turned 'off'' ($AgentPriority set to -1).
In addition, when Exporting to HTML or Exporting to Text (File menu), this invokes an once-only update of all running agents.
Detecting when manual 'Update now' is complete. In a very large or complex document with a lot of data and agents, where agent cycle time is a bit longer, it can be difficult to know when the full cycle is complete. A giveaway is that when the File menu's 'Update now' option is clicked, the menu clears but the 'File' caption remains highlighted in the main menu bar. Once the process is complete, the highlight disappears.
Considerations when using agents that query other agents. If you have a complex set-up with agents looking at the contents of another agents, it may take several manual 'Update now' calls to flush a change through all the agents involved. How many calls is down to the user knowing how they constructed their code. For the same reason, when exporting, it may be expedient to either leave the document for a while to update fully or make several manual updates before starting as the full export process only updates agents once.