1. Work out what all your monthly outgoings are - rent/mortgage, energy bills, food shopping, going out, gym membership, mobile phone, petrol etc. Be honest and realistic eg if you like to get your nails done each month, factor this in.
Put this aside into one account.
2. Work out what all your longer term outgoings are - car insurance if paid on an annual basis, white goods for the house, school fees for kids etc. Work out how much you need to put aside each month to cover these bills by the time they are due. To give an example, if your car insurance is 1,200 a year, you need to put aside 100 a month. Put this aside into another account.
3. Whatever is left, this goes into savings. Doesn’t matter if it’s 5 quid or 500. Put this aside at the same time you do the other two, so you aren't tempted to spend it.
This is the system that I’ve used for the last few years and it’s worked well.