What do I need to do each week/month/quarter/year?
The best advice I can give you is to make sure you put all your paperwork in one place, every day. Include printouts of orders made over the internet, bank statements and anything else you think you or your accountant will need.
Customer invoices, if produced, need to be tracked to make sure you are paid the correct amount and on time. List all invoices as you produce them, recording number, date, name and amount (net, VAT, gross if applicable). Then when the customer pays; add date, the amount paid and how paid. You can do this on a spreadsheet or in specialist software but if you don't record payments again invoices, you are likely to loss money. Writing the information on the invoice, while useful, does not make sure each and every invoice is paid, in full, on time.
Suppliers invoices: you need 2 files, unpaid and paid. Mark each bill with how and when paid as you pay them, not later you will forget. It is a good idea to have a list of what you owe and when payment is due. This information is needed to make sure you can pay, in full, on time.
Once you have all this paperwork you or your bookkeeper can add your data to your accounting system. If you do this at least once a month you will have the information required to run your business, identify potential opportunities, in time to take advantage of them or identify risks and manage problems.
If you are considering me to do your bookkeeping, you can give me the paperwork marked as above, either loose or with a summary. The more you do the less it will cost.
Your accounts will only be as accurate as the underlying data. Your data needs good complete paperwork to provide you with quality accounts to manage your business and reduce your accountancy costs.