Managing Update & Insert Transactions simultaneous

Hi All,

Below is scenario : 

Two transactions 1st Update  & 2nd second Insert (or vise-versa) running simultaneously on table.Due to this there is dead lock & eventually ending with process fail or error.

Here is what i am trying to achieve:

for Example :

If Updates comes in first then its should complete the Update Task and then start Insert.

If Insert comes in first then its should complete the Insert Task and then start Update.

Please help me in achieving this.

Thanks 

DGR