1. Financial record-keeping isn't as scary as many believe. You need good systems, a clear head, and a commitment to keep on top of the paperwork.
Do things regularly until they become second nature. If you are not arithmetically gifted, don't despair.
Just take your time, use a calculator and feel relaxed about asking someone else to check a row of figures.
2. Money people refer constantly to mysterious "books". All they amount to is the entries in the main accounts book or cash-book, supplemented by the bank statements, receipts for spending and evidence of any money received. Each transaction is recorded in the cash-book. If things are simple, you should just need the date, the amount, a brief note of the reason for the income or expenditure, and a reference number, such as a cheque number. Each month make sure that the transactions tally with the bank statement.
3. You might want to introduce analysis columns. Split the income and spending amount columns under different headings. Enter each amount in the most likely looking column. This way you can see and total what was spent on equipment, training, takeaway pizzas or whatever. Computer programs are natural for this kind of job, either as a simple spreadsheet or a purpose-built bit of software. If you are a beginner, it can be a good idea to run a manual system first, before going computerised.
4. Petty cash is a source of money that you dip into when you need some cash for official business. It may be petty, but you need to keep a tight control over it. The usual approach is the imprest system. It involves having an agreed float - 25 or whatever is appropriate, generally the lowest you can get away with. When you take money out of the petty cash tin, you leave a voucher - a sort of IOU, signed and dated. The contents of cash plus vouchers will always add up to 25. Vouchers should have receipts with them - so get into the habit of keeping bus tickets and receipts for small items such as pints of milk.
5. When the petty cash runs low, or once a week or month, you need to fish out the vouchers and replace them with cash totalling the same amount from the bank. Keep the vouchers and their receipts and enter the bank withdrawal of cash in the main accounts book. This way you perpetuate the brilliant system that there is always 25 in there.
6. Involve young people in all activities. They can do random spot checks on the petty cash box. They can countersign petty cash withdrawals. They can make decisions about what to do about discrepancies in the coffee bar till. The more open and transparent the system is, the safer it is, and the more everyone learns.