I think it all depends on the spirits themselves. I don't think you can carry on a conversation with them, but once in a while you may get a small comment back or something close to that. Thats why we try for evps when we investigate.
 

It depends on the people and spirits involved. I do a lot of evp work, and often get nothing or at best a yes/no answer to an innocuous question. OTOH, The first time I was convinced of the existence of ghosts was when I was at Prospect Place, trying to get evps at 5 a.m., and got a clear, direct answer to a question about home decorating! We have a very talented medium in our group who has come up with quite a lot of verifiable historical details through talking with the spirits that he could not have known beforehand. I have also started working with the Radio Shack hack version of a Frank's box and have been dumbfounded by the results. Among other things, I was able to get a spirit to repeat words to me in Chinese.

As for what to ask, I want to know more about daily life in the past. One of the spirits I work with through the Radio Shack hack is a member of a family from the mid-Victorian era whose mansion I now work at as a docent. I was able to get an answer out of him about whether an "accidental" death there in the 1860's was really a murder and some details about a past life connection to the place that he had been insistently telling me about psychically during the previous year. But in general, he's more likely to respond to questions about what I had for dinner than about the past. I'm trying to figure out why. I'm not sure whether it's a matter of privacy or if he thinks the past doesn't matter any more.

Overall, I do find that spirits are more likely to respond to questions about topics that interest them. After all, would you rather talk about your favorite hobby or answer interrogation questions about who you are and why you are there?

If anyone is interested in giving the Radio Shack hack a shot, there is information on my research with it up on www.eeriecanal.org under "Ghost Box Communication". It's well worth the $25 price of the radio to experiment with. I know I went from being a complete skeptic to "Holy, cow - this really works!"
 

When I do Evp work, I talk to them with respect as if they are there.. I get better results and they are more likely to respond in sentences.. I do not believe in provoking them, I would not like someone to do this to me in life.. The last location we did, we got over 85 Evp's and the responses where wonderful.. We must remember these people once lived life in this realm, and we have to try to respect the Spirit realm in which they live in now..