Without consulting a lawyer, you don't know what you are chancing. I hardly call that a good bet.
Not knowing how to get a lawyer or accountant is not a good excuse for not consulting one.
If you consult a lawyer for 1 project, you do learn from the lawyer and become a bit more knowledgeable for the next project and may not need to consult a lawyer a second time if the new project is similar.
Step 1 - Find a Lawyer:
1a. Ask people you know. For example, if at a company, maybe you can ask the legal dept for a referral for your personal project. Lawyers know lawyers. Even a divorce or real-estate lawyer will know other lawyers in different specialties or reputations of firms. Ask bankers, dentists, any small business people, etc. - they use lawyers too.
1b. Use Google. Call 5 lawyers and setup a meeting to meet them.
Step 2 - Interview them:
Interview them like you interview any potential employee. What is their experience with small IT projects? Are you small potatoes to them? What are their fees? Do they have legal associates to do the grunt work for cheaper than a legal partner (partner will still review and be responsible)? What do they suggest you to do for your side project? Ask why to see if they can explain themselves well. How well do you communicate with them? Do they respond to your emails or telephone calls quickly? Do they have other partners who can cover for them when they go on holidays or are busy with other urgent cases? Can they let you do some of the work such as incorporating and registering a trade name because it is easy (to keep legal fees low)?
Step 3 - Evaluate them:
As they work, get them send you all their documents. Read the legalese and ask more questions. Do they still explain themselves well. How long do they take to do the work? Attention to detail is important. If their work sucks or you don't communicate well with them go find a new lawyer.
Lawyers and accountants industries are whole mess on its own. When you come to lawyer/accountant, he is really interested to charge you as much as he can, which creates a lot of conflicts of interests, and whatever he is saying to you can't really harm him.
One has to take calculated risks, and do research on his own to not be screwed by lawyers/accountants.
(This can't be the actual answer, can it?)
Reputation is one proxy you can use for trying to gauge competency - ask friends, family, or coworkers if they have someone they're happy with.
Ultimately, there's a few big things they need to do, and you can try to evaluate those things instead or as well:
1) Clearly explain things you need to know. This might be making you aware of paperwork you need to file, tradeoffs between choices, rationale behind why they're suggesting you do something, or what the tradeoff is so you can make your own decisions.
Some (many? most?) lawyers are willing to do a free initial consultation, so you can get a feel for this in person, if you don't have a recommendation or don't want to trust only reputation. Basically: Can they communicate effectively?
2) Keep you out of trouble. There's a limit to what a lawyer or accountant can do of course, but a pattern of surprise financial difficulties, or getting into frequent contract disputes or lawsuits are a bad sign. The IRS frequently correcting an accountant's filings would be another.
3) Stay on top of things. Is the accountant filing taxes late resulting in IRS fines? Paperwork not ready when they said it'd be? Asking for the same information several times because they keep misfiling it? Going incommunicado for months when you have questions?
It seems simpler in practice: It came up in conversation that my friend had gotten his will done. I mentioned I needed to get my will done. He liked his lawyer, and was able to explain some about what he liked about her approach and give me her name. So I scheduled a consult with her on her website after trading some initial questions over email, showed up as scheduled, and then traded more questions at her office. I didn't know all the right questions to ask - mine were mostly of the form "uhh, so what do I do?" - but she was able to volunteer explanations about state inheritance law that put her questions for me into context. And then she had recommendations for things to do and why, as well as things she'd recommend not bothering with and why (and the contexts under which that could potentially change in the future), without being pushy.
Based on my answers, she drafted a will for me, and I was able to come back and sign it a month later when I scheduled it. I think I paid half after the initial signing but before she drafted the will, and the other half after the signing? Now I can recommend her to my friends, or ask her if she has any recommendations for an accountant, or even other lawyers for specialized needs.
Could I have done more to vet her? Sure. But I did enough for my tastes. Can't let the perfect be the enemy of the good enough and all that.