The way I do my budget is like this, basically: list every expense you have. Mark the ones that are the same every time (mortgage, car payment, insurance bills, etc) with a star (*). I make a little mark (~) for those expenses that are more fluid: phone bill may change, gasoline, food, etc. If you look back at the last 3 months of expenses, you can take an average and have an idea what you "have to" make right now.
I put aside the first 10% to tithes. The next 10% for savings. We put money aside for our retirement, college, and cash savings right out of the paycheck before we get it. Then go through all the * bills: is there anything you can do to change those? (Refinance, change companies, plans, or packages?) Write the ideas down and then go through all ~ bills: is there anything you can do to change those? (Coupons? Changing your routine so that you do your errand running on one or two days instead of running the roads all week, to save gas? Wash laundry or dishes on a different setting or different hours? etc, etc, etc--there's lots of ways to cut things here and there). Go through that checklist bit by bit and see how you can change the expenses every month just by tweaking your lifestyle or habits a bit. As you end up with more money leftover, do other things: build up a 6 month savings (what your monthly budget is, times 6), pay off all debt, we have a charitable gift fund for various projects we support, vacation funds, etc. Just because you have money doesn't mean it "needs" to be spent. We always have "projects" we're saving for, on top of normal savings and expenses. How much is acceptable totally has to do with where you live, your personal situation, your age, and how you live. My personal advice (just as a mom) is to not go with how much you should save necessarily, but how much do you NEED to pay the appropriate expenses. That is your budget. Then if you can stick to a conservative budget, you can figure out what to do as you save money. (But again: our health, life, dental insurances, our payment to our retirement account, our payment to the college fund comes out of the paycheck before we receive a check. Those are priorities in our household. The savings you can play with would be the "extra" money that you don't spend). Figure out what your priorities are, together. That way if you can't cover everything, you can see what's at the bottom of the list and the first things to get knocked out, at least temporarily. Get first things first. Good luck!