Low calorie alcoholic beveridges:
Light beer (a 12 oz Miller Lite has only 96 calories)
Gin and tonic (this is a personal favorite, not because it tastes good, but because I don't like the taste, therefore I drink slower)
Rum and diet Coke or Jack and Diet.
White Zinfandel (packs a good buzz in few calories)
Stay away from:
all malt liquor like hard lemonade, Hooch, Skyy Blue (270 cal/12 oz), Smirnoff Ice, etc.
White Russians or other cream/ice cream drinks
"fat" beer (as opposed to light beer)
anything with Grenadine (Tequila Sunrises are good without it), it's just pure sugar syrup
good luck! and remember that dieting can have some pretty drastic effects on alcohol tolerance, so take it very slow.