Your question is an important one.

Cutting the cable and the housing is easy. Doing it correctly is difficult.

The problem is cutting the housing. There is a special tool for cutting cable housing. If you don't have access to one (like at your friendly bike maintanance place), the best alternative I have found is a tin snips.

After cutting, it is crucial to make sure the cut end is in good shape. Use a file to remove any crushed part of the housing AND TO REMOVE ANY BURS FROM THE HOUSING END. If you do not smooth out the cut end of the housing, it will quickly abraid and damage the cable inside.

If you bought good expensive multi-wall cables, you do not need to lubricate. If you bought general hardware store brand cables, then squirt some grease into the cable housing before re-threading the cable through it. I use spray-can white lithium grease for this purpose because it is easy to slip the spray straw into the cable housing.

If you do not have white lithium grease, wipe whatever grease you have onto the cable and then slip it into the housing.