Discipline done properly is not adversarial and it is not complicated. It is a process, followed consistently, that gives somebody a genuine chance to correct what they are doing — and produces a record if they do not.
Small employers lose cases they should win almost entirely because there was no process and no record, not because the underlying conduct was defensible.
Deal with it early and informally first
Most performance and conduct problems are best addressed by a conversation, promptly, in private. Say what you have observed, say what you expect instead, and check they understood.
Then make a note of the date and what was said. Not a formal warning — a note. If the matter ever escalates, being able to show that the person was told months ago and had every opportunity is what makes everything afterwards reasonable.
Warnings
Where informal correction has not worked, or the conduct is more serious, a warning is the next step. It should record what happened, when, what rule or standard it fell short of, what is expected going forward, and what will follow if it continues.
Give it in writing, give the employee a copy, and let them respond. A warning the employee has never seen and does not know about is worth nothing later.
Warnings have a shelf life. A warning from three years ago should not be relied on to justify a dismissal today.
Be consistent
The most common way an employer loses is inconsistency. Two people do the same thing; one is dismissed and one is not. Unless there is an articulable reason — length of service, prior record, genuine difference in the circumstances — that difference is the whole case.
Write down your rules, give them to people when they start, and apply them the same way to everybody including the ones you like.
Serious matters need a hearing
Where dismissal is a possible outcome, a formal process is required: notice of the allegations in enough detail to answer them, adequate time to prepare, an opportunity to state their case and respond to the evidence, and a decision-maker who has not already decided.
In a very small business, finding somebody sufficiently independent to chair is genuinely difficult. It is a reason to take advice rather than a reason to skip the step.
Write it down as it happens
Dates, what was said, who was present, what was decided. Contemporaneous notes are worth far more than a recollection assembled afterwards, and assembling one afterwards is what most employers end up doing.
Ten minutes at the time. That is the whole difference between a defensible decision and an expensive one.
General guidance, not legal advice. Disciplinary and dismissal processes are governed by legislation and codes of good practice; take proper advice before dismissing anybody.