Installing fiber cement siding is an alternative to wood, vinyl and stucco. The cost is more than vinyl but less than wood and stucco, so it is a project that is cost effective than the former options.
Step 1 - Measure and Mark
Measure off the plank to where you need it and mark it off. Do several at a time so you can make the cuts less often.
Step 2 - Making the Cuts
Use a specialized blade used with the saw such as Mikita hardiblade or Dewalts filber cement blade. These are specialized to reduce the dust caused from cutting these planks. Use your eyeware and ear protection. You have to make the cuts very slowly. The advantage of using the circular saw is that you can cut more than one board at a time. If you are up on the scaffolding, using the guillotine or shears makes it handier because you can cut them up there. The guillotine is not unlike a paper cutter and takes muscle power to cut through as do the shears.