Hope I'm not moving this thread in a thousand different directions, but another critical, critical, CRITICAL, thing is figuring out what your "nut" is; how much you need to gross EVERY_DAY just to pay the bills. Things like rent (assuming you're renting a space,) electric, gas, COG, etc., are easy. Taxes get a little more complex. When you get down to pennies (office supplies, etc.,) and those pesky unforseen things (fixing/replacing tools, etc.,) it gets even more difficult.
I digress; anyway, having that number in your head is great motivation to keep the business streaming in. If it's Wednesday, you (just for a round number) know you need to gross $500 JUST to 'keep the lights on,' and you've only made $600 this week, you know you need to make some moves to catch up.
Also, I guess there are varying schools of thought on this, but in my very recent experience, marketing is critical ESPECIALLY in a slow economy. If you've got competition, your goal is to be the guy with the biggest market share at the end of the mess. It's easy to get trapped into thinking "nobody's spending money, so there's no point in wasting money on marketing." WRONG!!! You want to make sure any dollar anyone is spending on your type of product/service is spending it with you!
We've killed 3 competing shops in our area in as many years. Sounds harsh. I don't get joy in their failure. It'd kill me to have to close our doors. But "this town ain't big enough for the two of us." I think a constant, positive marketing presence has kept us alive the last couple years while the others failed, and we now have a 100% market share in our area.