this is usually very tricky. without sounding pompous, the best way to avoid bacnk charges is to stay within the bank's set criteria for lending. Obviously charges are cheaper on arranged overdraft facilties and normally customers are well informed of what charges will apply if they abuse their limits or take unauthorised overdrafts. Charges get very steep when cheques and direct debits are being returned, and basically banks can name their fees when this happens.
This situation should put people off getting out of control with their money.
We too have fallen into this trap before, but basically it became obvious that if we kept within their guidelines and allowances, bank charges were minimal and there were no suprises when we opened our bank account.
Banks can only help avoid charges if the facilties are not abused really.
Don't get too excited about bank charges being refunded either if facilities have been abused - it is a very long and drawn out process which I THINK ( but not sure ) is being reassessed at the moment.
It's not easy I know.