"I know where you're coming from" or "Do you understand where I'm coming from?" are comparatively recent expressions.
What did people used to say before?
And why do they have to be coming from somewhere?
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Perhaps people simply said 'i know what you mean'
d'ya know what I mean
d'ya know what I mean
Reference: Soozywoo
d'ya know what I mean
I understand. 
When someone says 'do you know what I mean?' it's like they're saying to me 'are you a bit thick?'. Yes, I know what you meant when you said you liked the pink shoes more than the blue ones.
Brisket you're proper deep man 
In answer to your question though; I don't know.
In answer to your question though; I don't know.
Thanks Karma
Reference:
When someone says 'do you know what I mean?'
Yes, and they often say it as part of their statement - before you have even had time to put a puzzled expression on your face. 
Reference:
Yes, and they often say it as part of their statement
Saying 'know what I mean' before actually telling you what is in question is indeed the very height of stupidity.
I know what direction you're coming from, brisket, but you have to think outside the box and examine the issue from all sides.
Myself? I'm not sure.
Myself? I'm not sure.
Well Blizzie that's a big help I'm sure
I can't multi-task.
I can't multi-task.
Reference: brisket
I can't multi-task.
Me neither! 
I'm just shuffling the papers of life.
Shocked confusion?
It basically means, I try to do as little as possible.