For assembly production, please offer gerber file, bom list, Silkscreen file and centroid file. You can see details or reference for some files below. 

BOM:  PCBWay BOM format

Silkscreen file: If there is not silkscreen on pcb, please offer assembly silkscreen drawing for assembly reference. On the silkscreen layers, please design the designators and polarity. For designators, they should match with the silkscreen on pcb; for polarity, these components should be designed clearly or easy to be distinguished, for example LED, IC, diode, tantalum capacitor and so on. Check below pdf for your reference.

https://pcbwayfile.s3-us-west-2.amazonaws.com/mail/19/08/14/1623550993447.pdf

Centroid file: its format can be excel, .txt or .pos. In the centroid file, X - coordinate, Y- coordinate, components angle, designators should be included, and please set the unit to be mm, check below link for reference.

https://www.pcbway.com/img/images/pcbway/a-sample-of-PCBWay-Centroid-File.txt  

Note:

1)How to generate the centroid file from different files?

Check below links for reference. Besides, we can help export centroid files from .pcbdoc and eagle files, so don’t worry if you can’t generate.
https://www.pcbway.com/blog/help_center/Generate_Position_File_in_Kicad.html

For production,

2) Centroid file (Pick & Place file): It is obligatory file you need to provide for SMD parts. If only THT parts, it is not needed

3) Assembly Instruction Drawing: It displays the designators, polarity of Diodes, Audios, LEDs, ICs and so on. If the silkscreen layer of pcb file is clear, it isn’t need to be provided.

4) Sample pictures of the assembled PCB: If you ever made it or you have 3D view, it will be the best reference.