At least once a week, a client asks me, "What else do you think I need to add to my invention to get my invention patented?" This is a hard question to answer. This is particularly true if the invention is related to a field I'm not completely familiar with (e.g., pharmaceuticals, very complex computer software, etc.). But even if I were an expert in a field, I'm still very careful about what I suggest.
This isn't because I don't want to help these clients. It's because I don't think it's in my client's interest to name me as one of the co-inventors. Although it may seem counter intuitive, an inventor is anyone who helps conceive an idea, even if that person isn't the one to ultimately make a prototype or perfect the invention. So if I were to suggest something that ultimately contributed to an invention, then technically I'd become one of the inventors, and as a co-inventor, I'd share the ownership of a patent with my client.
But there are situations where I help clients brainstorm by asking the right questions. This usually happens when a client is very close to enabling his invention, but hasn't quite gotten there. You really have to use your judgment in these types of situations. Usually I feel more comfortable with doing this when the client is an expert in the field and I know that he or she will ultimately come up with the idea on his own. What are the right questions to ask you say? Well, for starters, I ask things like:
"What is the most unique feature of this invention?"
"How is your invention different from what already exists?/ What different methods do you use?"
"Why are the prior art devices/methods disadvantageous?"
"How do you make this invention more efficient/better?"
These questions are general enough that I don't suggest anything, but are enough to get the client thinking. So, answer a question with a question. That might be in the best interest for both you and your client.