I work at a job and was wondering?

how do I learn how to make complaints more?And how much is it worth taking off of my employers before I realise that I should start looking for another job?I mean how do you know when an employer is talking to you too rudely and you should just get another job?But at the same time it's not always so easy, because in your head you decide to yourself that employers are just going to be rude if they think they should be rude and you know that you're doing it for the money anyway!