Scissors are more convenient than knives for some cutting operations. They obviously cannot be relied upon for perfect accuracy but are quick and simple to use for rough trimming, layout and paste-up work. Scissors with extended stainless steel blades that taper to a fine point and have comfortable molded plastic handles give greater control. Good quality, very sharp scissors are often quite expensive item but are worth the extra cost as they perform more precisely, last longer and can be resharpened when necessary.
A small pair, between 4" and 5" in overall length is ideal for delicate cutting tasks while an 8" to 10" pair is a good size for larger work. Always reserve you scissors for cutting papers, films and similar thin surfaces only. Thick boards, plastics and other modeling materials should be trimmed with a heavy-duty knife as they can easily blunt or even bend scissors blades.