This tip is simple…

Allow users to share your widget, without coming to your website.

If your ultimate goal is virality, this is an absolute must!

When a user who finds your widget on a MySpace profile, blog or any website for that matter, wants to copy the widget onto their own site… don’t get in their way. Don’t force them to come over to your website and signup.

I can’t tell you how many widgets I see out there that don’t do this.

Of course, there is nothing against offering additional benefits for users signing up for your service. For example.. RockYou has added incentive for people entering their email address when they create a slideshow.

“Why Should I Save?
Save puts your show in your MyStuff account so you can:
Save and edit slideshows
Get access to new, exclusive stuff!” — After creating a slideshow on RockYou

So external sharing of content, what does it look like?

Snapvine's widget pulls up the sharing UI after the audio has completed playing or when the user clicks the “share” button.
Snapvine's widget pulls up the sharing UI after the audio has completed playing.

YouTube’s external player allows for quick sharing of their content.
YouTube's external player allows for quick sharing of their content.

Plain and simple, pull out all the stops you have in the way of users wanting to spread your content and widgets around.