most good golf stores have a hitting area with demos. advice on a message board may be helpful, but there's nothing that competes with trial and error. as nightmare stated, make sure that the shaft flex fits your swing. i wouldn't go so far as to state that shaft flex is more important than the head, but it's integral to maximizing your swing. most golfers need regular flex shafts for their drivers.
unless you're carrying the ball over 240 yards off the tee, get a regular-shafted driver. a 240-carry distance means that your overall distance is about 260 or so. and i'm not talking about what you do once every round. i'm talking about what you do most of the time. the average golfer probably drives the ball close to 190-220 yards. i've seen a lot of average golfers. a lot. 90% of them drive nowhere near the distance they think that they do.
again, most good golf stores will also have a swing monitor that will determine not only which driver head is the best but also which flex is the best. if you're unsure, go with the regular flex--especially if you hit more slices, fades, and/or low shots.
rule of thumb: if you don't like it after five swings, you probably won't like it when you take off the price tag.
oh, by the way, get that driver cut down to about 43 to 44 inches (haggle to get that cut for free; also haggle for, say, some winn grips). most drivers are between 44.5 and 45.5 inches. that difference may not sound like a lot, but you'll probably hit a lot more fairways with a shorter driver. you'll lose only a few yards. you need a very fast swing/ball speed to realize the difference in driver lengths. even then, the difference is negligible.
just ask yourself: would you rather have a 6-iron (instead of a 7-iron) to the green for your second shot or a 30-yard pitching wedge underneath a tree sideways to the fairway? if you prefer the former, go with a shorter driver.
