What should I put in my seed summary?
When you seed a link, you're presented with a form that has "Basic Information" and "Optional Information". Optional Information is pretty important - it determines what Category your seed goes into, you can enter Tags, and you can also write a summary of the page you seeded.
If you copy and paste some text from the article into your summary - maybe you specifically want to discuss a key thought or paragraph - make sure you blockquote the words that aren't yours by using the blockquote button. It's the third button from the left:
Do not copypaste the entirety of the article as a summary. That's copyright infringement and will probably get your seed taken down.
From the Code of Honor:
Plagiarism and copyright infringement will not be tolerated. If you did not write something, do not portray it as your own (use the "blockquote" tag and cite your source by linking to the original content). If you do not have the right to republish the content in question, do not post it to Newsvine.