A couple things that are NOT vandalism.
- New users who don't know what they're doing.
- Incomplete pages that are poorly-written because the editor is placing the information in chunks, and not all at once.
- Disrupting articles on purpose.
- Completely translating a page into another language (for example, Portuguese, Chinese, Spanish, etc.)
- Adding nonexistent, redundant, and/or pointless categories to pages.
- Image Spamming
How to Block Vandals
If you are unsure if it's vandalism, ask the user to stop whatever activity is disrupting. If that user continues to do it, block him/her for (3 days, 1 week, 2 weeks, etc.)
If it's clearly vandalism, block for the amounted time shown.