when to use with(nolock) and with(rowLock) in sql server

I have the following code and i am getting error :- transaction process id was deadlocked on lock resources with another process  and has been detect as deadlock victiom


so what is the solution to remove this error

this procedure is use to save data in sale table




alter procedure Pro_Sale_Insert (  
@Voc_date datetime,  
@Party     nvarchar(40),  
@Sadd1     nvarchar(50),  
@Sadd2     nvarchar(max),  
@Po_no     nvarchar(30),  
@Po_date datetime,  
@Cform     nvarchar(3),  
@Fform     nvarchar(3),  
@Amount     decimal(10,2),  
@Tax nvarchar(10),  
@Tax_per     decimal(5,2),  
@Tax_amt     decimal(10,2),  
@Round_off     decimal(10,2),  
@Total     decimal(10,2),  
@Uname nvarchar(10),  
@Ref nvarchar(40),  
@ship_amt     decimal(10,2),  
@due_date datetime,  
@voc_no int output,  
@other_amt decimal(10,2),  
@pcode int,  
@gcode int,  
@type nvarchar(2),  
@BarCode nvarchar(300) 
) 
as 
Begin 
declare @Invc_no  int ,@op_date datetime ,@CallFrom Nvarchar(20)
set @CallFrom='Insert'
set @Invc_no=(select (isnull(max(Invc_no),0)+1) from sale with(rowlock) where gcode=@gcode) 
set @op_date=getdate()  
if(@type=2) 
begin  
set @pcode=(select (isnull(max(pcode),0)+1) from party with(rowlock)) 
insert into party(pcode,party,padd1,padd2,under,Ref,op_bal,op_date) values (@pcode,@party,'','','Debtors',@ref,0,@op_date)  
end  


set @voc_no=(select (isnull(max(voc_no),0)+1) from sale) 
insert into sale(Invc_no, Voc_no, Voc_date, Party, Sadd1, Sadd2, Po_no, Po_date, Cform, Fform, Amount, Tax, Tax_per, Tax_amt, Round_off, Total, Uname, ref, due_date, ship_amt, rec_amt, other_amt, pcode, gcode, BarCode) values (  
@Invc_no     ,  
@Voc_no     ,  
@Voc_date     ,  
@Party     ,  
@Sadd1     ,  
@Sadd2     ,  
@Po_no     ,  
@Po_date     ,  
@Cform     ,  
@Fform     ,  
@Amount     ,  
@Tax     ,  
@Tax_per     ,  
@Tax_amt     ,  
@Round_off     ,  
@Total     ,  
@Uname    ,  
@Ref, @due_date     ,  
@ship_amt    ,  
0 ,  
@other_amt,  
@pcode,  
@gcode,  
@BarCode  
) 
exec insert_sale_ledger @voc_no,@voc_date ,@pcode,@party ,@Amount,@Total,@Tax ,@Tax_amt,@Ref ,@CallFrom
end  
 
and this procedure is use to save data in ledger table


alter procedure insert_sale_ledger  
(  
@voc_no decimal(10),  
@voc_date datetime,  
@Pcode int,  
@party nvarchar(40),  
@Amount     decimal(10,2),  
@Total     decimal(10,2),  
@Tax nvarchar(10),  
@Tax_amt     decimal(10,2),  
@Ref nvarchar(40) ,
@CallFrom Nvarchar(20)=null 
)  
as  
begin  
  if(@CallFrom='Update')
  begin
delete from ledger where voucher='Sales' AND voc_no=@voc_no 
end 

   declare @under nvarchar(17)  
   ------------------------------------no1 ki entery---------------------------------------------------------  
   INSERT INTO ledger(voucher,voc_no,debit,CREDIT,party    ,nar          ,DATE     ,pay,nparty,under,pcode) VALUES  
      ('Sales' ,@voc_no ,0,@Amount ,'Sales A/c' ,'Sale Items',@voc_date,'True',@party,'Sales',2)  
 
   INSERT INTO ledger(voucher,voc_no,debit,credit,party    ,nar          ,DATE     ,pay,nparty,under,pcode,ref) VALUES  
      ('Sales' ,@voc_no ,@Total ,0,@party,'Sale Items',@voc_date,'False','Sales A/c','Debtors',@pcode,@Ref)  
 
   if(@Tax_amt>0)  
   begin  
     select @pcode=pcode,@under=under from vatcstNew  where party=@Tax  
     INSERT INTO ledger(voucher,voc_no,debit,CREDIT,party    ,nar          ,DATE     ,pay,nparty,under,pcode) VALUES  
        ('Sales' ,@voc_no ,0,@Tax_amt ,@Tax,'Sale Items',@voc_date,'False',@party,@under,@pcode)  
   end  
end  





and this is trigger to update stock 



ALTER trigger tri_salei_stock_add
on salei after insert
as 
begin
declare @gcode int,@voc_date datetime,@sku_code nvarchar(10),@Price decimal(10,2),@sale_qty decimal(10,3),@ser_icode nvarchar(1),@amt decimal(10,2)
select @gcode=gcode,@voc_date=voc_date ,@sku_code=sku_code,@Price=Price,@sale_qty=Qty,@amt=amt from inserted
set @ser_icode=(select sum(1) from stock with(nolock) where voc_date=@voc_date and sku_code=@sku_code and gcode=@gcode  
group by gcode,sku_code,voc_date)
if @ser_icode=1
begin
update stock set sale_qty=sale_qty+@sale_qty where voc_date=@voc_date and sku_code=@sku_code and gcode=@gcode 
end
else
begin
insert into stock(gcode,sku_code,voc_date,sale_qty,purc_qty,price)values (@gcode,@sku_code,@voc_date,@sale_qty,0,@Price)
end
end