2. Tumblr - A short list of random available usernames is shown
to help get the user signed up right away.
Don’t make visitors think too much

3. Show fields instead of a new page

4. Fewer form fields
Airbnb

5. Basecamp — When there is a form field error, the character on the left makes a surprising facial expression.
Use simple interaction to keep user filling the form

6. Use Storytelling

7. Kickstarter - The email sign up field proposes related email provider
is it thinks you may have mistyped your email.
Autocorrect email to reduce wrong address

8. Mailchimp - Reduces your price if you use two-factor authentication.
Offer incentive for visitors to signup

9. Apple Events - When adding Apple’s Live event to your calendar using their link,
It saves you the best seat in the house.
Offer incentive for visitors to signup

10. Trip Advisor - Users can automatically signed-in on promotional email
Make it easy for user to sign in

11. Optimised for mobile
Mobile users are five times more likely to abandon the task if the site isn't optimized for mobile

12. Grand St. - when you unsubscribe from their newsletter, they invite you to follow them on social networks instead.
Offer other alternatives

13. Quick feedback
Co Founder
Treating app- Asking the user straight away inside the app message

14. Amazon - “Thank you page”
Little things matters