Best format to use to scan, save and send illustrations



Can anyone advise me on the best way to scan, save and send images? I have been scanning my pictures (watercolours) as jpegs, working on them in photoshop and then sending them to the printer as jpegs. but the images are getting too big!! I am wondering if I would be better to scan and send them as TIFF images. Any advice on maximising quality while keeping image size manageable would be gratefully received. Thank you!