You have Checkbox Fields, Currency Fields, Free Form Text Fields, DropDown Fields Then you end up with something like:

nlapiSetFieldValue('custitem_nes_activeaafescom', 'F');

For Checkbox

nlapiSetFieldValue('custitem_nes_materialplating', '');

For Dropdown Fields

nlapiSetFieldValue('custitem_nes_weightprice','');

For Currency Fields...