Instead, I work on the principles that (1) I won't be too upset if I spend a fiver on a bottle and it turns out not to be too great, and (2) bottles on sale for a tenner are rarely unpleasant. When our wine stocks are a bit low, I therefore poke around the wine section of the supermarket for half-price ten(ish) pound bottles of wine of the general kind that I like. Sometimes it goes wrong but more often that not it seems to work out well.
The latest hit with this strategy was the "Zenith" Merlot/Cabernet Sauvignon/Shiraz blend from Kumala winery. A "juicy, smooth full bodied red wine", this one paired very nicely with beef and mushroom stroganoff. Very quaffable and a real bargain at only £5 from Sainsbury's - get some while it's still on offer!