What is the preferred/correct order for PP?

For example if a photo needs some curve adjustment, sharpening, cropping, straightening: which process is best done first, second, and so on.

Thanks

If you use adjustment layers for things like curves, levels, hue/saturation then it doesn't matter as you can move the layers if something isn't right. But sharpening (unless using capture or creative sharpening) should be done last.