What is the procedure of detecting errors in a trial balance that is not balancing?

Double-check your addition. Compute the difference between the debits and credits. Is there an account with that balance which was omitted from the balance sheet? Divide the difference in half. If there is an account with that balance, it may be shown on the wrong side of the trial balance (a debit balance shown as a credit or vice-versa). If the difference is evenly divisible by 9, there may be a transposition (ie, writing down 81 instead of 18 or 572 instead of 527). That transposition could occur in your addition, in an account balance or in one of the transactions posted to an account. If none of the above works, go back and check that each journal (ie cash receipts jounal, etc) balances and was posted correctly. Then check every other entry to make sure it balances and was posted correctly. Keep the difference in mind (and half the difference), that is the amount you are looking for.