Advance TT
A telegraphic transfer in advance (or part advance, balance against documents) is the simplest route and common for established or smaller orders. It keeps banking cost and paperwork light.
Letter of credit at sight
An irrevocable L/C at sight has the buyer's bank guarantee payment once compliant documents are presented. It adds security for larger or first-time deals, at the cost of some bank fees and documentation discipline.
How to decide
Smaller or repeat programme: advance TT. Larger or first contract where both sides want bank protection: L/C. Terms are written into the proforma invoice before production, alongside the incoterm. Start on the quote form.