How can employers discover the skills of the labor force and only commit to the labor force with experience?

If your question relates to Saudi Arabia then I must say it is difficult in the current environment with the5th November deadline fast approaching and all company employees need to be on a permanent contract and sponsorship.
Still there are some suggestion which I can give as follows:
1- In the standard labour contract there is something called a probation period which is normally for3 months in which you can discover the skills for the labour, but as I said earlier it would be difficult in terms of Saudi Arabia due to current environment.
2- You can have some Interview techniques or questionnaires which focus on finding out the particular skills which you are look for, also you can have some practical tests and exams through which you can judge them.
I hope this answers you question.
Kind Regards, Assad Siddiqi