Meal planning is vital, both to keep a rein on spending and also to get an overall balanced diet.
I use Quicken software (or try Money) to keep a track of spending - it automatically enters direct debits and standing orders, then a few times a week I sit with any receipts and type them in. You assign spending to different categories so you can quickly see where your money is going.
For irregular spending, like holidays, Christmas, car costs, children's music lessons etc, I work out the yearly spending roughly. Then I divide it by 12 and put that much money into a high-interest instant-access savings account. All the money is in the same account, but I keep a notebook allocating the money to different 'pots'. Then when I spend anything on those categories, perhaps to buy a Christmas present in September, I either don't put that month's money in the savings account, or if it's a larger amount, I move money back to the current account. So for example, our holiday was last month so the holiday 'pot' is empty and I start saving my monthly amounts for that this month. My Christmas 'pot' is very healthy, but will start to dwindle in the coming couple of months as I buy more presents. This helps us budget for the sorts of things that happen regularly but aren't every month.
For personal spending, we have a set amount every week which is 'free', although that includes clothes, miscellaneous expenses etc. What we do is have a notepad next to the computer, and every time my husband or myself buys anything, we write down the amount. So if by Wed or Thurs we can see we're nearing our limit, we rein in for the week. For bigger purchases, we make sure we spend well under budget one week to allow us to overspend the next. The notepad works for us because it's so easy to spend a few pounds at the newsagents, perhaps £10 on Ebay, £5-10 on a present and so on, and before you know it you've overspent. This way, we both can see instantly how we're doing. For bigger purchases, we consult and take turns if necessary if we each want to buy something more expensive.