I am a professional organiser. My top tip would be to plan, plan and then plan some more.
Meal planning is essential. I have an in use and a spare policy for everything. If you open the spare write it on the list and the shopping fairy will ensure it gets ordered. If you don't then do this then you will run out . Sorry slight "why aren't there any razor blades in the cupboard?" inspired tangent there...
I have a planning session every Sunday night (I call it the board meeting). I go through the calendar, my diary and DH's diary. I keep a file of dates that come home from school and add those in at this time. I do it whilst DH is gettting the children ready for bed. I shout up what kits are needed (swimming, guides, beavers, street dance etc) and he gets them ready and they are lined up in separate bags on coathooks inside the children's wardrobes so they can be grabbed as we go. Once I've synched everyones calendars DH and I go through the next 4-6 weeks looking for clashes and identifying who is doing school runs, guide runs, late school pick up, meals etc. That also goes on the calendar. This gives me a 4-6 week heads up if I need a babysitter / after school club / favour off another mum. We often text taxi drivers and babysitters at his time. We also open a bottle of wine and discuss where we're at with long term plans and we can discuss anything that is annoying us before it gets to the screamy hissy fit stage.
Paper work which DH needs to see goes in a file on his desk which he takes and reads on his journey to see clients (he goes on the train). He scrawls on it and I sort it out afterwards.
I run a bring forward system for the house. So, a school letter with three dates on it comes home. The dates go in the calendar. Then the piece of paper goes in the bring forward file for the first date. After that date, if it is still needed it goes in the file for the second date and so on. I have a monthly (Jan - Dec) file and a daily file (31 slots). So at the end of April I'll get out May's papers from the monthly file and allocate them to a day in the daily file. It sounds a lot of work but it actually takes 5 minutes a month. Each night I go to the daily file and takes out the next day's paper and put them on my desk to deal with the next day. It means that the letter about a school weekend trip in November with payment dates in September and October is always in the monthly file so I don't lose it and I don't have to see it for months on a noticeboard. It will appear in September when I need to do something and then I refile it in October ready for the next action. I file holiday brochures in there too. We usually book our Summer holiday in April so any useful brochures, newspaper clippings etc go in the April section. Likewise my car insurance is due in July so if I see any good deals they go in the July section. I also use this for chasing people. So if I write to HMRC and want to chase them in a fortnight I put it in a slot in a fortnights time. I don't have to remember where the paper is and the bring forward system will remind me when I have to do something. If I need it in the meantime I know it will be in the file and I can lay my hands on it is 20 seconds.
I have a pretty box on my desk which has all my projects in and I take an A4 folder, put everything in the folder relating to that project and store it in the box. It's out of the way but I know where things will be. I only use this for things which have no date attached.
Receipts go in a large envelope in the hall. At the end of the month I seal the envelope and date it, start the next envelope and file the old one. I also shred the one that is now a year old. So at the end of April I will seal April 12's envelope and file it, shred April 11's envelope and start May 12's envelope. I only do this for day to day receipts as I have a folder for bigger purchases. So a washing machine receipt goes in the folder, with its manual and guarantee and a petrol receipt goes in the envelope.
Gosh sorry mammoth post.