Finding a great accountant or an attorney is actually pretty hard and this is coming from a tax accountant. You'll find that finding a good professional is going to be difficult in the same ways.

- Questions
Great questions to ask a tax or legal pro is to go for the throat. What specific experience does he have in your industry and to name a few clients. Most desirable professionals won't lie about their experience and if they do, checking references will make sure they stay honest. I believe everything you say, until I learn otherwise from checking. Having specific experience is key because it doesnt matter how many years of general experience they have unless they're able to understand your situation specifically. I've seen a number of "generalists" miss big obvious pain points on tax returns and legal issues.

- Potential Red Flags
Inexperience and lack of professionalism. Tax accounting and law is fundamentally based upon experience (even the law that controls the two professions is based upon the concept of "precedence" or "experience"). No one learns how to be a great tax or legal pro. It takes years to develop the necessary acumen and understanding behind the madness. Also, lack of professionalism is when the pro doesn't have pride in his work and half-asses his work. You can generally sense this from their behavior but obviously you can always get tricked. But, usually the half-asses will make enough experiences that even you'll notice. The problem is that you usually notice when its too late haha.

- Certifications
They're required by law to practice tax and law. But, other than their legal requirement its useless because it fails to tell you anything besides they've met the basic requires to cram words into their photodex brains with mass quantities of caffeine and adderral.
Awesome example: Everyone looks for a "CPA" to become their accountant expecting an experience tax professional. Problem? Did you know that a CPA or an accountant's function breaks down into two major dichotomies? We're either auditors (fact checkers) or tax guys. Wanna guess what you're CPA is? CPAs are traditionally auditors by trade and they generally outnumber the tax guys. I cant tell you how many times I've met clients with crap ass CPAs because they never knew to CHECK WHAT THEIR EXPERIENCES WERE (see the first question). All they knew was that the CPA is certified and worked at some sexy big 4 (KPMG, PWC, EY or Deloitte). Big mistake.

- H&R Block
Would you outsource your code to india? Enough said. I generally ask every client to bring their tax returns for the prior 3 years if I learn that they've been to HR Block. Ive found money left on the table 10 out of 10 times.

- Directories
Yes they exist. No you won't use them. Ever.

- Specialization
You're talking about a field that specializes in minutia. In tax and law, every small detail could make or break your specific situation. Ex. Sales tax. Professional software that is provided on tangible property (CD or some other tangible media) will be taxable. Generally professional services are not taxable but in this situation, your screwed.

- Lawyer
Refer to the first question. Anyone can review these things but obviously experienced professionals could find potential issues that aren't obvious. But, if another site or program has a similar function then you can probably just copy their terms.

Sidenote: I'm really surprised at the number of questions the HN community has for accountants and lawyers. I think i'm going to start a podcast on my blog to answer these questions. Anyone interested (i've already bought a blue yeti and etc so its kinda late to ask but I love new tech toys haha)