MVP testing - what metrics should I record?

I recently launched a small MVP. It's a web app which is supposed to make file uploading easier, without the need to register, use complicated UIs or have porn popups be thrown at you ( ;) ).

Right now I have some traffic getting into the site. I'm trying to record as much as possible, but I don't understand - how can I know which metrics are important so I can get my validated learning running (yes, I just recently read The lean startup)?

Any ideas? Thoughts?

What are your assumptions? Write them down, then figure out how to measure them, then start measuring. Get a couple thousand uses then review your assumptions with measurements. Determine if you need to change your assumptions.

+1 for #leanstartup

What do you want people to do on your website?

1. Upload file -> Measure the percentage of visitors uploading a file

Work at improving this number.

2. Share the file link with others -> Measure the number of visitors (other than the uploader) to download the file

Work at improving this number.