Written warning is part of a PMP (Performance Management Plan) that every company implements to improve the output, metrics and professionalism of its employees. This is being given to those who are having issues or breaches with the company rules and regulations including poor performance at work. If you've got one and you want to go through it, here are the steps that will help you.
Be calm
Signing on a written warning is hard to swallow especially if it is your first time. Having a warning doesn't necessarily mean that you are an incompetent person which is why you don't need to react badly. If you've been caught on doing a violation, you need to accept the consequences and learn from it. Breathe and try to understand why it you are on this situation. Ask your supervisor if there is something that is not clear to you. Remember that the main purpose of warnings is to serve as a reminder or a platform for improvement and not as a threat or punishment.
Know the reason
Determine the root cause or the obvious reason why you have been placed under a Performance Management Plan. Your supervisor will explain the details to you and you have to remember the points that are being explained to you. It could be because of your tardiness, absences, poor quality, insufficient output or a house rule violation such as use of mobile phones in restricted areas.

Avoid the same mistakes
Written warnings have different levels and each has a corresponding period of effectiveness. If you committed the same grounds while you have an active warning, your PMP will escalate to the next level and this could lead to termination. Check on how the escalation process goes with your direct supervisor or the human resources department.
Move forward
If you have received a written warning because of your performance, research on how you can improve it. Study and train yourself about different processes depending on the type of your job. Ask for tips of your colleagues or you can work it out with your manager. Set a goal and when you are at the highest point, be consistent.
Always remember that PMPs won't be implemented by companies if it is doesn't guarantee improvement. It may sound negative that you have received a written warning and it could be worse if someone else finds out. This humiliating feeling will turn into something good once you have learned from your mistakes and you have pushed your better self out.