when I started my firm, I talked to some of my clients and found out what insurance agents they were using for errors and omissions insurance. I picked one from a list of about 3 insurance agencies. My agent shops premiums among several insurance companies to get the best deal. Over the last 7 years I've had insurance with DPIC, Zurich, RA&MCO, and Beazley.
Sometimes, when you are starting out, you can lock your premiums for the first 3 years to avoid the customary year-to-year premium increase. The difference in premiums from the 3rd to the 4th year might give you sticker shock. My premiums jumped from about $3000 per year for the first 3 years to about $12000 per year at year 4. Luckily, my business was good so I could afford the rates. Subsequent yearly increases were not that bad. At year 7, I'm paying just under $15000. My agent shops me around each year and was able to get my rates down from just under $19000 last year to the $15000 this year.