When you have new chicks coming from the post office or from the incubator you need to be prepared. Chicks need 90 degree temps to stay alive. They can't get chilled. If you don't have a heat lamp, go to the hardware store and get one or maybe more depending on how many chicks you are getting. If you have too many chicks for one heat lamp they might bunch up too much and then some babies could get trampled. No fun.
Heat lamps can be dangerous. Many fires have been started with heat lamps. Make sure your heat lamp is very secure and isn't close to anything like wood chips or walls, that could get too hot. Be careful! I know there are options that are not heat lamps, I just don't have anything to recommend for you. Do some research!
24 hours before your chicks arrive you need to prepare their brooder box or space where they will be for a while. We put down an inch or two of wood chips on the floor. Put paper towels or rags over the wood chips. Until those chicks know that what real food is, they will eat little wood chip particles. That's not good. Could kill them if they eat too much wood chips. After a day or two of eating chick feed, I don't worry about them eating wood chips.
When you bring your new farm babies home. You need to get them warm and drinking water. Don't give them food for at least an hour. Dip their beaks in warm water so they know to start drinking. The hardware store also sells chick waterers. We like the gallon waterers for when the chicks are just a couple weeks old or less. If the tray where the water sits is too big, you will have little drowned chicks. Add a couple marbles to the water tray. Your chicks will be curious and they will peck at the marbles in the tray and drink more water that way.
Here is my homemade restorative water boost that I have used from my favorite chicken guru, Harvey Ussery. He has a great book called the Small-Scale Poultry Flock. I rarely lose chicks when I use this amazing recipe.
Homemade water boost:
1 gallon warm water
1/4 -1/2 cup honey
4 Tablespoons raw apple cider vinegar
4 cloves of garlic, freshly squeezed with a garlic press.
You can also buy a little bag of chick water electrolytes that you can add to the water, that works just fine. Ask for it at the hardware store. Remember your new baby chicks could be stressed when they come in the mail. If they get some sort of boost through their water, they will recover a whole lot better.
I want to recommend the book that I just mentioned. Harvey Ussery is so knowledgeable on how to care for a backyard flock! I learned so much from his book! Information that I had wondered, but didn't know how to get my chicken questions answered. Plus that, you can't just trust anybody on the internet! :)
It is very important to have time to check on your chicks multiple times that first day. Hopefully you planned well and have time to observe them. If they are all huddled under the heat lamp, they are probable chilled. If they avoid the heat lamp, the heat might be too intense. Raise and lower accordingly. You can lower the temperature by 5 degrees each week until your chicks are old enough to not need the heat or your outdoor temperatures are warm enough for them.
After an hour or so of drinking water, your chicks are ready for some chick food. Your handy dandy hardware store will have some pre-made chick feed all ready for you. Again, I hope you prepared ahead and already have it. Last thing: Over the next week or so your chicks are susceptible to pasted vent. That is where their back end will get clogged. You will see a glob of hardened chick poo stuck to their back side. No biggie. Take a wet warm cloth and loosen it, till it comes off. Pasted vent happens a lot more when your chicks have had to travel a long distance or when they have gotten stressed! I also think if you give feed too early and they haven't drank enough water, they are more likely to get pasted vent.
Good luck with those new farm babies! They will bless you with some amazing eggs or nourishing meat in a few months! I never want to be without chickens on my property! Chickens are one of the basic farm critters that you can't farmstead without!