I am moving from the 5C to the new 6S. I want to give away my 5C. How do I get all my stuff off the phone, like find my phone and other personal stuff?
Is it easy to set up the new phone. I have backed up my old phone to Itunes

If you have iCloud backup turned on it should be backed up there.
Just do a manual backup before wiping it.
To be sure though (and if you only have the free 5GB of storage in iCloud and the photos won't fit for example) plug it into a PC or Mac running iTunes and do a backup to that.
That will backup everything including all the photos.
Backup to either one will backup all personal settings, wifi networks email accounts and content (POP3) and all app content (all entered data in an accounts app for example or the local notes in the notes app).
When you have the backup done just go to Settings/General/Reset and select Erase all content and settings.
This will return the iPhone to it's factory state.

As has already been said backup the phone locally using iTunes to restore to the 6s. If you make the backup encrypted it will copy all your passwords into the backup (otherwise you will have to enter some of them again!!!) You could also use iCloud backup but I prefer a local one for this purpose!

Just restore this backup onto the 6S and everything will be as before!

"Erase all content" will insist that you disconnect the 5C from iCloud before it will work. After it has completed the 5C will be in a fully wiped state and ready for sale.

Here's what I do before I sell any iDevice:

Turn off find my iPad / iPhone
Log out of iTunes
Log out of iCloud
Log out of Spotify
Remove from my Apple devices
Delete iCloud account

Thank You all guys. Very good of you all.

BKM is correct. probably better to use iTunes. It's safer and a lot quicker (unless you have 100Meg broadband).
Also the point about making it encrypted is something i forgot. Saves a lot of faffing about with passwords.