Have a brooder set up, with a heat lamp. Have the heat lamp set lower than usual-- as hot as 110F directly under the lamp is fine for this. (Not a brooder plate. Not anything temperature-controlled that is meant to stay at just the "right" temperature. For this, you really do want a little bit "too hot.")
Other than that, have feed & water ready, and something non-slippery on the floor of the brooder (paper towels work well, but are not the only option.)
When you get the chicks, take them out of the box and put them under the heat lamp. If any are almost-dead, put them under the heat lamp too (not the very hottest area, but a little bit out.) The healthy chicks will probably huddle under the heat lamp and peep, as if they are still cold. Just let them do that, and fairly soon they will be warm enough to start exploring and finding the food and water. For the almost-dead ones, if they are still laying there, turn them over every now and then so they can warm up on all sides. They may just die, but I have seen some remarkable recoveries as they get warm (to the point where it was not clear which chick used to have the problem!)
As the chicks get warmed up, they eat and drink and start to move away from the heat lamp. It is important to have a big enough brooder that they can get away from the heat when they want to. Within a day or so, you can raise the heat lamp to provide more normal chick-brooding temperatures. If you want to use a brooder plate, make sure the chicks are doing fine for two or three days and then give it a try.
I have not dealt with chilled chicks very often, because they usually arrive just fine. The hatcheries are usually quite good at packing the chicks so their own body heat will keep them warm in the current weather (smaller or larger box, less or more vent holes, etc.)
I have sometimes seen advice for sugared water (to provide quick energy), or electrolytes in water, or various other helps. I have not used any of those, and I have not personally seen any situations where I think they would have made a difference. They may help in some cases, but I don't know enough to tell what times those would be.
Note, other people may have other advice. What I said is what I would do, and have done in the past. It worked fairly well for me. Dead chicks stayed dead, healthy chicks stayed healthy, some almost-dead chicks recovered.
