Generally, you want a comprehensive evaluation of your child, not just a brief interview that bases conclusions on general impressions. Be skeptical of an evaluation if they claim they will get you in an out in an hour with a diagnosis. A comprehensive evaluation should include:
a developmental history addressing the pregnancy, birth, and attainment of milestones
a detailed discussion of your concerns across all areas of development
extended observation and interaction with your child
information from as many sources as possible: parents, teachers, childcare providers or others who know the child well and see the child in different settings or circumstance
direct assessment of your child's abilities should usually be a part of the assessment process; this should include measures intended to tap both strengths and limitations.
Some providers may offer you a wraparound, or Best Practice evaluation (BP). A BP is necessary for initiating wraparound services and periodic reevaluations are required to maintain wraparound services. However, a BP was not originally intended to determine if an autism spectrum diagnosis or other developmental disorder applies. The BP was originally developed to assess the needs of adolescents with severe behavioral and emotional disturbances. Managed Care Organizations, who pay for most BPs, require a very specific and detailed format for determining the need for wraparound services, much of which may be irrelevant to a young child for whom an autism diagnosis is being considered. In addition, the BP format may not allow sufficient time to assess developmental concerns and rarely include direct assessment of the child. A more comprehensive assessment is recommended to determine diagnosis and levels of functioning.