Here are screenshots of OBJ export settings that work with octane, please share export settings for apps not yet in this list and I will pop them in this post.
3DS Max
3DS Max
Blender
XSI
On a related note, here is what to do when importing into octane...
To make sure that scale is correct, you should select the units that you have been modeling in, for example in you modelling app, if you have been modeling 1 unit = 1 cm, you should select CentiMetres in the dropdown box in the import preferences, which can be found from the file menu.