Most clone losses happen in the first three days, in the grower's room, not in transit. This is the short version of getting them through it.
Day one
Unbox immediately. Do not leave them sealed overnight.
Low light only. 18 hours at a distance, dimmed, or a T5 a foot away.
Humidity 65 to 75 percent. A dome is fine if you vent it.
Water the plug, do not feed. Plain pH-adjusted water at 6.0 to 6.3.
Day two and three
Expect some droop. It usually lifts by the end of day two.
Start venting the dome for longer stretches each day.
Still no heavy feed. A quarter-strength veg mix at most.
Transplanting
Wait for visible new growth at the top before you pot up. Roots chasing the edge of the plug is the signal. Transplant into a small container first, not straight into a five gallon.
Common mistakes
Too much light too early. This is the number one killer.
Feeding a stressed clone. It has no root mass to use it.
Letting the plug dry out completely, then flooding it.