first when you calculate the salary you have to put first figure as gross salary which means what you received in F.Y. 2013-14 total amount of salary including perks,perquisites,areas etc etc)then you have to put amount under sec.10(calculation of exemption requires here) and then deduction under VIA. after all the process you will received taxable amount from you have calculate tax then edu.cess. By doing this you will get total tax payable amount and if you have any relief u/s 89(1)(on arrears) then you have to less from total tax payable. now you have final tax amount. less from tds,tcs,advance tax. at the end you have payable or refundable amount.
16 May 2014
above is the process of calculation of the income tax.
but for your Query
1, yes you have to take both salary & arrears in your ITR even if your employer don't give you form 16 or not mention in form 16. (for employer they must have to show proper amount in Form 16)
2, you don't do that if you received arrears in f.y. 2013-14 then you have to show that amount in f.y. 2013-14 also. you cannot take into f.y. 2014-15. yes, you can avail relief of sec. 89(1) if arrears is not received for same f.y. but its all about calculation how much amount you will be take as relief.