How to decide whether the amount needs to be dr or cr

all expenses and assets having debit balance...i.e it should be debited..

for eg:

1.rent paid                           1000

2. furniture purchased.           5000

journal entry:

rent (exp) ac dr 1000

      to bank/cash*       1000

furniture ac dr    5000

      to bank/cash         5000

all income and liablities are having credit balance... it should be credited

1.furniture sold          4000      bank/cash ac dr      4000

                                                     to furniture acc         4000

2.creditors                 500          bank/cash ac dr    500

                                                        to creditors            500

In simple

p&l left hand side and assets = debit balance

p&l right hand side and liablities= credit balance

For more clearance go through golden rules of accounting 

Regards,

Harish Ragav

I do it this way,

Remember that

1. debit=deposit=jama and credit=withdrawal=naame.
2. debit cash and bank accounts when money is deposited in them and credit when money is withdrawn from them.
3. similarly, debit assets/stock accounts thinking that assets are deposited when you purchase them and withdrawn when you sell them.
4. in case of capital accounts, if you owe money to A it means that you had taken money from A at sometime. So, debit the cash/bank account and credit A's capital account in case of a loan and vice-versa. You can also think that you are withdrawing/crediting money from A's account and depositing/debiting it in your accounts.
5. when you make an expense you are essentially spending money from your cash/bank. So, you need to credit the cash/bank account and therefore debit the expense account while making an expenditure entry.
6. when you earn income you are essentially getting some money either in cash/bank. So, you need to debit the cash/bank account and therefore credit the income account while making an income earned entry. 
7. when you take a liability/loan, you are obtaining money from other's account. So, debit the cash/bank/asset account and credit the party's accounts while taking a liability.

When you come across a transaction try to break it down in simple terms and you will automatically understand how to make entries. Don't try to remember formulae for this. Just give it time and practice.

I am giving below two links of  two videos which clearly explain the rules of debit and credit.

https://www.youtube.com/edit?o=U&video_id=OlpjtCWO130&feature=vm

https://www.youtube.com/edit?o=U&video_id=OlpjtCWO130&feature=vm

In case you still have some doubts you may visit www.jbsclasses.com and I will clear your doubts.