Well, for one any honest and reliable appraiser will have some sort of credentials behind them, and will more than likely be a member of an appraisers group (Like the ISA, International Society of Appraisers). If they have nothing to back up that they are qualified (a appraisal degree), do not use them. They are not a legal expert or properly trained, no matter how much "experience" they claim to have. It's like going to a "doctor" who had never been to medical school.
Once you find a few qualified furniture appraisers, then you can meet with them, either in home or at their business front. Many will work in or own a antique or furniture shop, and will have a store front you can visit. Many will also be willing to come to your home to give a quote on how much the appraisal will be. And just because someone doesn't have a store front, doesn't mean if they have real qualifications, that you should disregard them. Being a independent appraiser is a highly profitable career, and many do not feel the need for a additional income from a store so they work from home. Be sure to ask each one about the rates and how they charge (by the hour, by the piece ect...), and request client references. And do check up on the client references to make sure they do their job right. After that, it is up to you to make the decision on what appraiser to use, based on qualifications, client references and fees.
Also, if you have anything outside of furniture that needs appraisal (like art, coins, sculptures, jewelry), you will have to find a different appraiser for those items. Appraisers specialize in a field, and don't have enough knowledge of market values and other items in general to appraise them