A large number of threads over the years have explained how to build your client base. There is no magic bullet or a guaranteed list of non-AMC clients. Most of the suggestions have centered around beating the bushes and offering your services to local banks, credit unions, attorneys, real estate agents/brokers, etc. Services can range from helping out with a listing amount, assisting a buyer's broker in coming up with a value, providing a buyer or seller with value information, divorces, inhouse mortgages, home equity loans, etc. You need to work hard and build your reputation as the go to person when it comes to valuing real estate and the real estate process in your marketing area. The goal is to build a level of trust with other real estate professionals who are comfortable relying on you being an independent voice of knowledge and reason.
I probably spend close to 10% of my time talking about real estate issues with agents/brokers and lenders. While this time doesn't result in direct compensation it is well worth it as whenever I contact one of them for information I receive great response time and a lot of valuable information. I also get a lot of referral work from them. Since the first of the year one local broker has provided me with more than 15 referrals which have resulted in 11 appraisal assignments totaling more the $20,000 in revenue.
As far as AMC work that is a choice everyone needs to make for themselves. By choice, I have never worked for an AMC. Not saying I never will but at this point I am able to stay busy enough and earn enough money that I don't need to be responding to all of the scope of work and time demands. I price my work based on location (required travel) and complexity, typically offering a two week turn time. I enjoy the variety of my work which over the last several months has included vacant building sites, single/multiple family dwellings, bars/restaurants, build to suit national chain stores, motels, golf courses, etc.