my best tip is about bills.
every time i receive an invoice, i put it into a sheet "bills that need paying"
invoices are paid at the end of the following month, so eg April's invoices will go on May's page.
each time i get a bill for a monthly charge (eg, notice of direct debit schedule for elec) i put all the details in each month that it will be taken.
then at the end of that month (eg april), i order them all by payee, and pay them in one go.
then when (may) comes, at the bottom of the list, i put details of all receipts of purchases in that month.
my headings are:
to whom, for what, invoice number, amount, vat amount, how paid, bank details (you only need to fill these in the first time) contact details, extra information.
i highlight them as i pay them in purple, and email them to confirm payment.
when i do my VAT return, i add them all up (invoices are vat'ed the month before) and use them to calc my vat.
at the end of the year, i add them all up for my tax return.
i also have a spreadsheet of daily takings, which is filled in every day when i cash up, and again, added up for the relevant returns.
doing this not only means you have a ready reckoner of expenses/income, it also means that you don't have to sift through hundreds of bills and invoices at the end of the tax year.