As per SA300...Planning an audit involves establishing the overall audit strategy for the engagement and developing an audit plan. The objective of auditor is to plan the audit so that it will be performed in an effective manner. Once the overall plan can be developed to address various matters identified in the overall audit strategy, considering the need to achieve the audit objectives through efficient use of auditor’s resources.
As per SA320 ...materiality means the amount or amounts set by the auditor at less than materiality for the financial statements as a whole to reduce to an appropriately low level the probability that the aggregate of uncorrected and undetected misstatements exceeds materiality for the financial statements as a whole. If applicable, performance materiality also refers to the amount or amounts set by the auditor at less than the materiality level or levels for particular classes of transactions, account balances or disclosures