For a couple of months keep a little book with you and write down everything you spend. And I mean everything. Group your costs together and see where you could cut back. Then plan what you will spend when and stick to it. Try and build some treats for you all in too.
How you budget will depend on where you spend. For eg, if you find you're spending on silly small things at the beginning of the month when you feel like you have money, look at saving some money into a separate account soon after payday. If you splurge in the supermarket, consider online shopping where you can watch the running total and you're not so tempted by impulse bargains.
Hope this helps.
AG