Thread by @ChinweikeE

employment letter, pay slip or bank statement showing your salary, tax papers if possible, your resume' reference letter with correspondence address with which they can contact your employer, etc.

These documents are to be submitted to an assessment body that will look at them and then give you either a negative or positive assessment.

Note that the assessment is not done by the immigration department, but an assessment body. Each profession has their own assessment body. Just like we have COREN for Engineering in Nigeria, NIM for management etc, Australia has such bodies that u'll have to submit ur docs to..

After submitting these documents, they examine them, contact your employer either by mail or phone call, and when they're satisfied they give you their report as either negative or positive. If it's positive then you can claim the point for work experience.

For engineering, they have Engineering Australia (EA), while for agriculture and a couple of other fields the assessment body is VETASSES.
For those do not have work experience in their field of study or not long enough.
But there's always a way out.

Like if you studied microbiology but don't have the work experience, probably you've been working in the bank you can't do assessment as a microbiologist or banker either. Your skills must match your work experience.

What you need to do is contact a lab or any microbiology related service owner/employer and let them provide you with the relevant documents.

On special arrangements you can explain to them the purpose and ensure that whomever you're going to put his/her name & contact is someone that can answer their questions and explain to them your role in the firm, as stated in your resume' because they'll definitely be contacted.

They should be able to arrange those documents for you with evidence of salary payment that can reflect in your bank account, where this is not possible, an affidavit will do, stating that you were being paid by hand/in cash.

If you must do this ensure that you're thorough with it, don't leave any loose ends, don't leave any room for doubt or your assessment will come out negative.