If you smoke, don't bother trying to quit. You're already in a position to be miserable, and your attitude is now your greatest asset. You should, however, buy the cheapest, foulest, most nauseating cigarettes you can find so that a) you rate of consumption will go down and b) instances of people bumming off you will go down, both saving you money. You'll only smoke when you really need one, and nobody will bum off you more than once.
Secure some form of reliable transportation. If you don't have a vehicle, your work options are severely restricted. Depending on your situation, public transportation may or may not be an option. At one point for me it wasn't, so I worked two jobs within walking distance. If this is you, walking distance now means at least two miles, better four. A reasonably fit person can walk four miles in an hour. But remember the vehicle doesn't have to be yours, it just has to be reliable. If you can really rely on family and friends, do so, but make sure you pay your fair share of the gas, and don't think of borrowing the car or bumming rides as your right. It's not. Be grateful someone is willing to help you out.
Sort out your housing situation. Boils down to four options really. Your own place, a semi-permanent place with someone else, couch-surfing with friends and relatives, or sleeping in your vehicle. No, sleeping under a bridge is not an option. You might as well go get yourself a shopping cart and start collecting cans. Once you're that far down you should be contemplating how you can get locked up while avoiding maximum security.
Which one is best for you boils down to how much you can afford. More on how to figure that out later. Suffice to say, if you're already in a place, renting or with a mortgage, you need to do everything you can to stay in that place. There are only two ways to come up with enough money to do so: Increase what you earn or decrease what you spend. Probably you'll need to do both.
If you can't stay where you are and have a semi-permanent place you can go (family, good friends), make sure of two things: That where you are going is not psychologically unhealthy (many families are toxic) and that it affords you good opportunities for work. Wherever you go, don't stay there for free. That's psychological poison. To the best of your ability, you need to stand on your own two feet for your own sake.
If you have nowhere to go but have a vehicle, you're still all right, relatively speaking. You can maintain your independence, and keep working. You have two main concerns: Safety while you're sleeping and keeping presentable. Getting killed is a piss-poor way of getting out of poverty, so you need to choose where you park to sleep carefully. It's better to get woken up and harassed by a rent-a-cop than park somewhere more private, but much less likely someone will hear you if you scream. Which reminds me; if your vehicle doesn't have an alarm, get one. They're cheap, especially if you can do it yourself. And Do It Yourself is what you're all about now. You should also have a mobile phone, both for 911 and because you need to stay as connected to everyone and everything as possible, for jobs, for family, for friends, for sanity.
How you stay presentable is quite straightforward: Laundromats and free showers. Laundromats are self-explanatory. Free showers are where you get creative. You might have friends who will lend you their bathroom. A YMCA membership is cost-effective, with the plus of getting you out of your car and doing something healthy during off-time. If worse comes to worst, soldiers have been bathing in staggeringly awful conditions for a long time. You can stand to do a quick sponge bath in a gas station sink upon occasion. Just make sure the door locks.
A word about living out of your vehicle: Keep everything organized and clean at all times. Your life is full of enough chaos and confusion as it is. Don't make it worse by finding your last pair of clean underwear wedged behind the gas pedal.
A word about pets: Make other arrangements for them. You have to take care of yourself now, so you can have the chance to take care of them later.
A final thought about living out of your vehicle: Spend as much time as you can in public settings. The price of a cup of coffee is a small price to pay to stave off the inevitable sense of isolation that comes with vehicular sleeping arrangements.
In any case, don't fall into the motel trap. It's a fool's game. If you've made enough enough for a motel room for a night or a week, odds are you're only two months away from having you're own apartment or rented room. Sure, it'll probably be a shithole, but at least the sheets won't have been splooged on by truckers.
Work. If you don't have a job, your job is now to find a job. If you have a job, guess what? You don't make enough there, or you wouldn't be in the situation you're in now. You need to be doing two things: Looking for a second job, and looking for a better job.
You'll probably need two jobs. Consider one in the food service industry, so that you'll know where at least one meal a day is coming from. Don't whine or complain, even to yourself if you work two jobs. What are you going to do with your off time? Endlessly admire the corinthian leather seats of your mobile abode? Watch Jerry Springer?
Every dollar you earn is a rung on the ladder you will use to climb out of the hole you find yourself in. Every dollar you spend is a rung taken away. Make sure you spend for good reason: Health, safety, sanity, or as an investment in yourself (haircut, alarm clock, etc.)
Always be on the lookout for beauty. In a sense you are no longer part of the community; you've gone into the desert. Now is the time that real meaning is most likely to appear. Be ready for it.
Keep clear in your mind a series of concrete, achievable goals. "When I have $xxx I can put a deposit on an apartment." "I made it through the week with $xx to spare." Don't let your routine turn into an endless loop.
Pay back people, fuck corporations. People are real. Corporations are faceless money-eating machines. The guy that loaned you $20 for gas will likely suffer down the line if you don't repay him; the bank that ate your house is getting bailed out by Washington as we speak, and the CEO that ran the company into the ground is getting millions in severance pay. Now is not the time to worry about your credit score. Now is the time to worry about your dignity and humanity.