I am what I believe to be the world's only Entrepreneur in Residence in a law firm (at least I haven't found another so far). I am a lawyer by training, but spent the last 25 years or so as a serial entrepreneur. I joined one of Canada's largest and most international law firms a few years ago to provide commercialization and financing strategic advice to early stage entrepreneurs and to assist Fasken Martineau in figuring out how "big law" does business with these companies.
In my experience, you need a combination of a trusted advisor who you can build a long term relationship with, who, if they haven't walked a mile in your shoes, are able to understand the practical issues involved in running an early stage business. Price is often a factor, as a result, we have instituted a "law firm as a service" subscription model as well as fixed fee pricing to address affordability and certainty.
Lastly, and most importantly, an advisor with a network who can advance your business is critical. Most lawyers can handle the technical legal work, however, very few can open the doors that you need opened.