Seeing things from the point of view of an attorney can be very useful. Other stereotypes about experts include the use of legalese, big words and convoluted sentences, being of a certain age, and even adhering to a certain dress code. Although a physically older appearance can be used in a positive way, I have seen situations where the primary issue was the use of appropriate comparable sales and analysis. The appraiser's age and length of professional experience did not have any bearing because the appraisal report was faulty. Big words and convoluted sentences can put the jury and judge to sleep, not to mention that you will not be a good advocate for your estimated value.
Clear communication is the key.
Another myth is that an expert witness must be from out of town to be any good. This is often the case in smaller communities with a highly unusual situation or property. This can be refuted by demonstrating your ability to grasp the significant factors in the particular situation or property - even if you are local. Your professional image as an expert in the field is reflected by your ability and willingness to identify and use resources to complete an assignment. Of course, the assignment should be within your comfort level.