files, such as photos and documents, then use:

1. Dropbox - comes with free space;
2. Google Photos - use this to back up all of your photos from your Android or iOS phone for free. Unlimited storage for compressed files and limited storage for "original" size photos.
3. OneDrive - They have free space or unlimited space if you have an Office 365 subscription.
4. Google Drive - also comes with a decent amount of free space.

If you want to backup every single thing on your computer, I suggest using an online service, such as Crashplan for about $5/month.

Backup is very important to me, as I am mostly paperless for home and for my work. My backup strategy is this:

1. My important documents are backed up on Dropbox. Always available even if my house burns down and always available on all of my devices.
2. My photos all go to Google Photos. Unlimited backup for precious memories. Free.
3. TimeMachine Backup - I backup everything to an external hard drive automatically.
4. Crashplan - $5/month - just in case all of the other backup methods fail for one reason or another.

The biggest thing you want to do with you backups is have it done all automatically without having to worry about it. Also, it's important to have a backup offsite in case of fire/flood/theft, etc.