The first thing to do when buying an apple device is to set up your iCloud, what is iCloud?
iCloud is a way that apple uses to make the orchestra working together, if you have few apple devices everything will be synced on them the same way, to create an iCloud account you can use your traditional email, no problem, or the one that comes when signing up for iCloud, I'd rather use my Gmail account. To create an account you can do that from the internet www.icloud.com or the easiest way is to do it on your mac from /system preferences/iCloud , or even on your phone. There's several options you can choose , the one in the picture below are the ones I choose and I will explain why.
iCloud Drive → ON ⇒ WHY ? Because you can store simple files and have access the same as Dropbox for free, the total iCloud free space is 5GB, if you have more stuff you better not to put it there, is just useful when you make a text file or small files so that are all synced between devices.
Photos → OFF ⇒ WHY ? Because I personally take a lot of pictures and the 5 GB free space from apple is not enough I have terabytes of pictures and it will cost me too much, I store my pictures on iPhoto with the library based on an external hard drive " take a look to the article how to put your iTunes and iPhoto libraries on an external drive .
Mail → ON ⇒ WHY ? Because I don't use a lot the iCloud mail and it won't waste a lot of space the email I get on my iCloud mail.
Contacts → ON ⇒ WHY ? Because it's fantastic that your contacts are all safe and will appear on all your devices magically.
Calendars → ON ⇒ WHY ? Because I use it a lot, and I can put an event on my computer and with alerts and I will get it immediately on my iPhone, iPad etc..
Reminders → ON ⇒ WHY ? Because my brain is linked to reminders, every idea I have I write it down here and it will be synced with all my devices
Safari → ON ⇒ WHY ? Because I use google chrome so it won't use iCloud space and it's nice to have a safari backup just in case your going to use it.
Notes → ON ⇒ WHY ? Because same reasons as the reminders.
Passbook → ON ⇒ WHY ? Because Plane tickets and cards are all safe and won't waste too much iCloud space.
Backup→ OFF ⇒ WHY ? Because I have too much stuff and I rather back up my stuff on an external hard disk, time capsule or several hard disks. It also slow down the computer the ON option and it'll imply you to buy iCloud storage if your rich go forward.
Keychain → OFF ⇒ WHY ? Because I have my passwords encrypted in files on several different locations on my computers and hard drive.
Find my phone → ON ⇒ WHY ? Because it's the most important iCloud feature from here you can see where your devices are, you can block them , you will have the certainty that none but you will use your device if lost, you can even make it ring if your loosing it in your house, you can log in from every computer and control your devices, how ? on www.icloud.com /LOG IN/ FIND MY PHONE>PASSWORD AGAIN> TOP CENTER CLICK ON DEVICE AND THEN THERE'S OPTIONS, picture below !!
PLAY SOUND → it will play a sound if you lost in your house.
LOCK → it will lock it if stolen and send you a message with the location when turned on
ERASE MAC → It will delete completely your device, to do when you want to sell it !
When signing in for iCloud your devices are turning into free calling and texting machines between Apple devices, you need to configure your iMessage app on mac, and messages config. on iPhones, iPads etc.. The following picture is for an iPhone, it can be found on settings, same for Facetime. when sending a text then if the message bar will turn blue the other person has an iPhone and it will be free, to make free calls (data required) you can use facetime video or facetime audio.
When going on address book the facetime block will add and the phone icon is audio call, so it will not waste your data plan and the video icon is video and it will completely drain your data plan so I recommend to do it always under WiFi.