Asking the right questions can help tax preparers avoid many issues with problematic clients.
With a bit of skill, many of these questions can be presented in automatic fashion, via an interactive form on a website. This can prove advantageous for both preparer and potential client, as it can reduce the need for time spent waiting for in-person meetings.
The questions presented are only a guide.
Different tax preparers may have difference preferences and risk tolerances.
Those specializing in tax resolution, for instance, may actively seek out clients with back taxes, while others may not. Others specializing in foreign currency transactions may not have any interest in R&D issues.
The more aggressive the client, the more likely he will push for questionable approaches and push back against your judgement.
Some potential clients will intentionally provide misleading answers in order to convince an accountant to accept them as customers. For this reason, it's often wise to push clients to self-select by pointing out policies that they may not like. Saying that you charge more than the average accountant may quickly cause low-value customers to end sales discussions before much time is wasted as part of your sales pitch.
In some cases, accountants can gain great insight into clients by looking at their financial statements early in discussions. Some accountants are even known to look through financials to see what potential clients have paid previous accountants and other service providers to get a feel for how much they should charge.