General Alignment Considerations
Some designs will require less precise alignment than others. If you have split an embroidery so that the split lines go between all the stitch areas, for example if no connectors were used, it is unlikely that you will need to have perfect alignment between sections. The main consideration would be to ensure the fabric is straight each time it is re-hooped.
However, when any stitch areas are split, alignment is crucial to achieving a good stitchout. Using alignment stitches and compensation of Low or High will help to align sections and eliminate gaps between them.
There are also various alignment aids including:
The printed full size template
Worksheets for each section, optionally printed on transparency paper
The hoop template supplied with the hoop for your machine
Light sensitive pens that can be used to mark fabric, and other temporary fabric marks
Fabric stiffening aids and stabilizers that combat pull and make alignment easier
The needle and embroidery positioning controls on your embroidery machine