While you can always manually format the text within a Note, if you often start your notes with a title you can have them automatically begin with that formatting. To do so, head to Settings -> Notes and tap on "New Notes Start With." You can choose between Title, Heading and Body. Title is a bold large font, Heading is bold and slightly smaller than Title, and Body is normal text.
iOS 10 finally adds the ability to share your Notes with others, allowing all invitees to view and make changes to them. Whether you are sharing a checklist with others or just adding to a doodle, this is a welcome improvement. To share a Note it must be in the iCloud folder (as opposed to the "On My iPhone" folder). Start a new note and tap the silhouette icon next to the Share icon (despite its name, the Share icon isn't used for this particular type of sharing, but for messaging, Tweeting, etc.).
Notes created on your iPhone can now be moved to your iCloud account if you need to free up space. Here's how:
In the Notes app there are two main sections listed in the Folders section: iCloud and On My iPhone. You can move notes stored in the On My iPhone section to iCloud by tapping the Notes panel listed under the On My iPhone section. This will allow you to see all the notes stored directly on your device.