So here is how I print the inserts for myself.
My printer is just an HP Inkjet, a slightly older one, it is a HP Photosmart C5280. (Considering how old this thing is I was astonished that they released new drivers last year.)
I use HP Brochure Paper - Glossy, but I'm sure any high quality paper will do.
http://www.amazon.com/HP-Brochure-Glossy-Brightness-Q1987A/dp/B0000BW6V6/ref=sr_1_1?ie=UTF8&qid=1462049872&sr=8-1&keywords=hp+brochure+%26+flyer+paperWhen I print I make sure my printer is set to Best quality and Print at Actual Size.
Make sure the print size settings are set to 100% scale and the Height is 12.25 cm and the Width is 15.5 cm. This is slightly larger than an actual jewel case insert because of the cut marks in the image.
Then I move the print position of the image to the top of the preview sheet. This is so I can print 2 inserts per sheet of paper. (Allow a few min drying time before sending the paper through the printer again.)
I use scrap booking tools similar to what TDIRunner posted to cut the paper.
When I fold the inserts I don't score them, I don't trust myself not to cut through, I just lay them over a jewel case and fold them over the top or bottom edge. Then when I put the insert into a case I use a finger nail push the fold into the corner and this usually makes a good crease.