3 - very accomplished; exceeds expectations
2 - meets the criteria for the assignment in all significant respects
1 - demonstrates some attempt to meet the criteria, but is inadequate
0 - no significant attempt to meet the assignment criteria

We would often expect an assignment that is deserving of full credit to score a 2 in this scheme.

Examples:

Summary of an Article: 

3 - captures the essence of the article, written in very good English
2 - displays a general understanding of most of the important points of the article, written
      in readable English
1 - shows an attempt to read the article, but demonstrates insufficient understanding of
      key points, or is written in a slapdash or incoherent manner
0 - no indication of any comprehension of the article

Theoretical or Mathematical Assignment:

3 - correct work, clearly and elegantly presented and explained
2 - mostly correct work, with at least some explanation if called for
1 - generally incorrect, or completely lacking in necessary explanation
0 - incorrect, with no evidence of any understanding

Programming Assignment:

3 - clear, elegant, and well-documented code that correctly solves the problem
2 - at least workmanlike code that handles most aspects of the problem
1 - rubbishy code that produces only partial results, or sort of reasonable code that
      doesn't work at all
0 - no progress in solving the problem