Pine is much softer than maple but good to practice on.

Everyone before me has already mentioned the end grain sanding where there are usually factory machine marks going in a direction different to the grain. Best to ignore the direction of machine marks to begin with and always sand in the direction of any grain until that method has eliminated all machine marks and scratches. This may take you up to 180 or 240 and once all smoothed out you can then start sanding along the edges or across the end grain to bring it home. At this point 240 is good if you plan on staining as that still allows colour to soak in, 320 is smoother but maybe not as much colour penetration, 400 is probably too far gone unless going for a solid colour. Maple necks are usually quite smooth straight out of the box and don't need much sanding if planning to stain that too.