1. Impact Identification. The method chosen must be able to address the full range of anticipated effects and identify specific environmental parameters of importance. It should allow for isolation of project-specific effects as well as short-term and long-term effects.
2. Impact Measurement. Explicit indicators are needed to measure the magnitude of effects. Where easily measurable indicators do not exist, other forms of measurement can be substituted as long as objective rather than subjective measurement is stressed.
3. Impact Interpretation. Because some effects may be small in magnitude but also important or far-reaching, the significance of effects must be assessed. This requires that criteria for the determination of significance be developed and explicitly stated. In addition, assumptions upon which the criteria are based must be stated explicitly. Some measures of significance involve judgment, so it may be important to provide a means for the public to have input into the process.
4. Impact Communication. The end result of the methods chosen is an overall assessment of the effects of an activity. As a result, methods must provide a means of highlighting key effects and/or issues for both the public and decision-makers. In the end, it is the method and its results that can provide a common ground for discussion and decision.

Please note that most methods do not exhibit all of these characteristics, nor do they exhibit them in the same manner or with the same effectiveness. Thus, it is a matter of trade-offs involving scale of a proposed development, anticipated effects, and costs. The table below summarises the differences and some of the trade-offs.

= Meets criterion

? = May meet criterion or can be adapted to meet criterion