Firing, sacking, letting go or terminating people is unpleasant. There are ways to minimise resentment, but why bother? Because most legal action and unpleasantness stems from dissatisfaction/resentment about the way things were handled - about how rather than what happened. Dismissal can be unfair because of the reason, or the way it was done, so you need to be extremely careful. In the law regarding employer-employee relationships, fairness is key. You must be fair, and be seen to be fair. But fairness, like beauty, is in the eye of the beholder - after being terminated, very few people have clear vision!
Prepare a disciplinary process/policy given to all, with a sequence of verbal then written warnings ending with dismissal. Ensure processes allow for discipline/termination on grounds of both performance (capability) and attitude (conduct). Specify your right to instantly dismiss someone (summary dismissal) for gross misconduct, and give guidance on what would constitute this.
Have hard evidence to back up all decisions. Documentation of poor conduct and/or capability is essential. You have to follow your own process to avoid legal unfairness. Negative appraisals/reviews make good evidence.
Never take decisions lightly - weak performance can sometimes be improved by skilled intervention/support. Termination is traumatic/demotivating for surviving staff, even when they understand why.
Avoid surprises by giving every opportunity for improvement before opting to terminate. This reduces grounds for legal action. Plus, survivors feel less threatened if they see you are fair. Employees who have been aware for some time there is a problem are usually less traumatised, and may already be looking elsewhere. Always avoid firing someone who has no idea its a possibility, except for summary dismissal.
Get legal advice if you have any questions. Balance