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A risk might happen; an issue has happened. Mixing them makes the register useless, because a list of things that have already gone wrong is a status report, not a forecast.
When a risk occurs it becomes an issue and leaves the register. That transition is the point at which most registers stop being maintained.
What might happen, roughly how likely, what it would cost, who owns it, what you will do about it, and — the part usually missing — the trigger that says it is happening.
Without the trigger, nobody knows when to act, so the mitigation is executed after the fact if at all.
Few enough that somebody genuinely watches them. Ten beats forty.
The trigger. Without it nobody knows when to act on the mitigation.
One named person with the authority to act, not the project manager by default.
Half an hour with your own data usually saves reading three of these. The guides will still be here afterwards.