- cell phone: don't get one if you can't afford it (ditto for a regular phone)
- kids: if you can't afford them, use a condom (yes, that's harsh, but that is something that really beats my understanding, people already living on the edge that decide to have one, two or even more children)
- in general: if you can't afford something, don't buy it.
Your prior decisions will determine to a large extent whether or not you can survive on a very basic salary when hard(er) times hit. Getting a room-mate and sharing the cost of things that you are unable to afford by yourself are good tricks to get around some of the more practical limitations that a low wage job gives you.
I used my low wage job (mailroom boy) to expand my knowledge about computers which eventually landed me a higher wage job. My typical meal back then consisted of plain macaroni with ketchup, because the rent took away 5/7ths of my income, and the electricity bill another 1/7th. That left me with a grand total of 100 'credits' to feed myself for a month. Not a whole lot. I made pretty sure that there were no kids, phone bills or debts to go with that, and I did whatever was within my means to cut short that phase of my life.