By the glass? The standard is for the restaurant to offer only a few wines by the
glass - most of the wines they have (especially the good ones), will be by the
bottle only.
Sadly, after plenty of practice, I subscribe to the opinion that there is no short cut to picking good wine. Why would there be such Kudos about being able to do so if there was a secret trick? (like the secret tricks revealed in 'how to pick up women', and similar impossible enterprises).
So... its practice, practice, practice. You'lll pay 1/3 to 1/2 the price at the store for a good bottle of wine - I recommend buying good wine to drink at home maybe once a week - try something new each time - try something else from the same vinyard as another wine you likes and explore the similarities - buy several wines made from the same grape and compare. Enjoy the process rather than aiming for an 'end result' (ie, appearing to know what you're doing in a restaurant), and you'll find yourself sitting in a restaurant in a few years time and knowing what half the wines on the menu will likely taste like - and hence be able to match them to the food - and hopefully impress your date (or was it the waiter you were trying to impress?).