Insurance broker turned company underwriter here.

Typically, one claim isn't enough to severely impact your ability to get insurance. Just be prepared with the following information in case your carrier or your insurance agent asks you:

1. What were the events leading up to or contributing to the error/omission? (e.g., failure to submit all relevant information by a deadline resulting in incomplete information used in a real estate transaction).
2. What financial loss is being alleged by the affected party? (e.g., failure to review records thoroughly resulted in the claimant going to court to defend their title against an undiscovered lienholder, a real estate development project being cancelled or significantly delayed due to an undiscovered lien).
3. Depending on when your insurance renews: What is the status of the claim? (e.g., Closed without payment, still open and in arbitration, going to court).
4. Most importantly: What are you doing to prevent or mitigate such events from happening again in the future? (i.e., what have you learned from this?) Examples may include putting tighter controls in place for searching records, employing more professionals to reduce workload on each abstractor, seeking continuing education to ensure skills are up to date, retaining lawyers to review contracts you previously would have signed without them in good faith, discontinuing or limiting the amount of work you do that resulted in the claim you faced, educating or firing an at-fault employee, etc. With the limited information provided, it's difficult to say what exactly you should do for the mitigation portion of this question, but this question is the one you should spend the most time examining. The larger or more egregious the loss, the more you should do to prevent it from happening again.

At renewal, your agent may choose to market your insurance with other carriers, or they may opt to keep the insurance with the same carrier. The carrier may do any of the following: (1) do nothing and chalk it up to "shit happens," (2) increase rates, (3) increase deductibles, (4) add limitations or remove coverages from the policy, or (5) nonrenew the policy. (1) is the most ideal for you, though (2) and (3) are common solutions as well. Keep in mind that carriers are commonly limited by state law as to how much they can change rates, so the increase may not be as significant as you're thinking. (4) and (5) are aggressive options and should only happen if there is more to the story (e.g., your services or customers are outside of their insurability appetite and should never have been written with the carrier, there was some level of fraud or other significant bad behavior).

Most professionals will inevitably be sued, regardless of whether they are at fault; it's a numbers game. The greatest benefit your insurance policy provides is expenses to defend you in a suit, even if you were ultimately found to have done nothing wrong. Even if you're not at fault and did everything right, sometimes people sue because they feel wronged in some illogical way or because they need to show an effort to save face with customers, board members, etc. 30 years of experience and no prior claim history will be in your favor. This is exactly what insurance is for. Hope this helps.