A lot of the non-chain local wine shops have Friday night tasting sessions.
They are free - you just need to look like you may buy some sometime, and perhaps do so occasionally.
You get to taste small amounts of several wines and over a period of weeks can compile your own list.
Or as JAS said, tour the regions. There are many places were there are several wineries very close together.
The approach varies - Nepenthe, Hahndorf Hills, and Shaw+Smith, are very close together, and at the first two you just stand at the counter, look at the list, and tell them which you would like to taste.
The other one charges you $14 and serves you a few wines with the cheeses they think are appropriate.
I think that is a bit pretentious of them, as well as being perhaps an attempt to save on self-promotion costs.
So, I said, " No thanks!" and went to the next one down the road.
[I figure I'll decide what I eat and when, and I was there to taste wine not cheese.]