I only ever drink white wine, but I'm usually offered a taste regardless of whether it has a cork cork, plastic cork or a screw top.

If I asked the waiter/waitress if I could try it before I bought it, then yes I would want a taster first, but usually I just order a bottle using my rudimentary wine knowledge to select the one that I would like the most. Unfortunately my rudimentary knowledge is often greater than the person serving me (certainly in the UK, very less so on the continent); I was in an Italian restaurant last week and ordered a bottle of Verdichio, the waiter asked me 'the sparking wine?'. I said 'I don't think it is unless there's something wrong with it'. Good job it wasn't otherwise I'd have looked pretty stupid.