this is a good question and something i've struggled with for a while. i don't like to give info because i need to know they aren't cold reading me, but i have found when you don't give some sort of frame of reference, they can start talking for a while without "connecting the dots".
i'll admit - i am a little TOO open with my go-to's. i give them too much info sometimes, because i know they have been good in the past so there is no need to waste time seeing what they'll pick up. it seems though, that the more info you give, the more the reading can take a certain path. i may be wrong about that, but that's what it's seemed like with me.
i will give an example of a recent call i made to Source Power. she is someone i had used a couple times before. i thought she was good on one occasion, and not good on the other. it had been like 6 months so i decided to call her again. i asked how a trip over the weekend would go for me. she went off on this long tangent about things that didn't really seem to make sense. then starts like, getting frustrated and saying - i don't know what it is you want to know here! you just asked me about a trip, but i don't know what it is you are looking for, what you want to know, etc etc... just kept talking without letting me get more specific. she isn't cheap, so i got a little irritated with this. i told her where i was going and the purpose of the trip (it was a fun trip for my bday, but before she kept picking up that i was making lots of contacts - which seemed more business oriented). anyways, when i told her where i was going and just said it was for fun she changed her tune a lot. the reading changed to fit with the place i was visiting.
the problem is - it's so easy to cold read people when you are giving up some info on the situation or person you're asking about. even when readers say something like - "when was the last time you spoke to him". that gives them the ability to see how long its BEEN, therefore, how long it may be in the future. if you haven't talked to him in 6 months, then more than likely you may not hear from him in a while. or if it was last week, then it's likely you will hear from him this week. stuff like that. granted, i imagine it must be hard to just look at a person, their energy, question, etc and get a complete story or picture - esp on the phone while the clock is ticking. so, i just don't know..