Usually, this means telling your direct boss of your decision to resign both in writing and verbally. If you have a written contract, it should address the amount of notice that you are required to provide. In the absence of this contract, give reasonable notice. This can vary from two weeks to three months in most cases, depending on your length of service, responsibilities and the degree of difficulty in replacing you. Don't take anything.
Most employers are very concerned about company property and confidential information.
If it doesn't belong to you, leave it with the company. Even in the absence of a written contract, there are implied legal obligations on every employee not to take, use or disclose confidential corporate information. You could expose yourself and your next employer to costly litigation if you fail to abide by these obligations. Honour your contractual obligations. Avoid making your own assessment on legal enforceability.