Economic growth,interest rate and exchange rate policies are the crucial determinants of remittance inflow. Based upon it a valid instruments need to be used. There are many papers that can be found easily in Google-Scholar.
Beside the mentioned-quality points of Amish - Rauniyar, safety of mail-transportation, security of banking related documents, and the transnational networks of hacking-tracking would be other crucial determinants in our current global era.
I suggest to you the following articles that deal with the determinants of remittances. As you can note, the determinants are various and linked to the scope of analysis.
1) Remittances and the brain drain revisited : the microdata show that more educated migrants remit more
Albert Bollard, David McKenzie, Melanie Morten and Hillel Rapoport
Policy Research Working Papers, World Bank
November 2009
http://dx.doi.org/10.1596/1813-9450-5113
2) Migration and remittances during the global financial crisis and beyond
Ibrahim Sirkeci, Jeffrey H. Cohen and Dilip Ratha
Book
May 2012
http://dx.doi.org/10.1596/978-0-8213-8826-6
3) Forecasting migrant remittances during the global financial crisis
Sanket Mohapatra and Dilip Ratha
Policy Research Working Papers, World Bank
December 2010
http://dx.doi.org/10.1596/1813-9450-5512F
4) Determinants of remittances: recent evidence using data on internal migrants in Vietnam
Yoko Niimi, Thai Hung Pham and Barry Reilly
Policy Research Working Papers, World Bank
April 2008
http://dx.doi.org/10.1596/1813-9450-4586
5) Remittances : transaction costs, determinants, and informal flows
Caroline Freund and Nikola Spatafora
Policy Research Working Papers, World Bank
September 2005
http://dx.doi.org/10.1596/1813-9450-3704
6) Migration and remittances: causes and linkages
Yoko Niimi and Caglar Ozden
Policy Research Working Papers, World Bank
December 2006
http://dx.doi.org/10.1596/1813-9450-4087
7) The demographic, economic and financial determinants of international remittances in developing countries