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

Show fields instead of a new page

Fewer form fields

Airbnb

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

Use Storytelling

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

Mailchimp - Reduces your price if you use two-factor authentication.

Offer incentive for visitors to signup

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

Trip Advisor - Users can automatically signed-in on promotional email

Make it easy for user to sign in

Optimised for mobile

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

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

Offer other alternatives

Quick feedback

Co Founder

Treating app- Asking the user straight away inside the app message

Amazon - “Thank you page”

Little things matters