Kanban's first principle is "Start with what you do now." and iterate from there. So, what you want to visualize is completely up to you, based on what you do today to track data about your work items.
If you have absolutely no current process/ practice regarding something, start somewhere - take a decision as a team that "we will visualize these things on our Kanban board and each ticket". These become your initial "policies" that you can change in the future, depending on how well they work for your team.
Some of the ticket design options suggested by the Kanban University material are shown below -
(C) Kanban University (earlier Lean Kanban, Inc.)
These are also suggestions - nothing is 'prescribed' - it is up to your team.
We use Kanban for our product development - and here are things that we visualize -
Of course, different teams can choose to visualize different things on the board and at the card level.
In general, as Todd has mentioned, how granular do you want your board and cards to be depends on what you are trying to track on the board and at the card level - what is important to your team and your stakeholders.
On a couple of items that you have specifically mentioned, here are my thoughts -
Visualizing "external work" - work being done by another team. This assumes that some work on YOUR board is held up (blocked) due to an external dependency. This should be visualized by having a blocker on the card (such as the red blocker on the bottom-right corner of the second image above) - with some description or comment to let team members know why this is blocked.
A team member is helping another team member do their work. This can really happen in multiple ways - and depending on how often this happens, how much of their own time team members are spending working with someone else on THEIR tickets, and how long does it take them to work on others' tickets, etc. If it is very minimal, you could have WIP Limits on your board columns (or individual WIP Limits) to accommodate a person working on multiple tickets at a time (whether they block their own ticket or not - policy item!). If a significant part of a team member's time goes in helping others, then you definitely need explicit policies on how they deal with their own work (block it, move it to a "Waiting" bin, etc.) and how their contribution is recorded on the others' tickets (such as having two people assigned to that ticket while both of them work on it, etc.)
You could also have policies such as "Anything that takes less than 15-30 minutes need not be recorded on the board/ ticket". It depends on how often this happens.
Other than the above, in my opinion, a Kanban board should visualize the following -
- WIP Limits on each lane and column
- WIP Limit violations if you allow them, and
- Card-level flags for Issues, Risks and Blockers
- Class of Service associated with tickets (this can be done in multiple ways)
- Work-item type
Here are some options on how boards might look - Boards organized by activity type or by teams.
Or, a board organized by class of service shown below.
Here is an article on board design that might help you - How granular should my kanban board be?. You may also find other useful resources in our Kanban Guide.