I think the best to dress for your age is to understand your style personality. I think being in your 40's, it's important to get more serious about the way you dress. Skirts should get a little longer and nothing funky. You should have a pair of good fitting denim jeans, a few crisp cotton shirts in white or neutral colours, a great little black dress; a few merino wool sweaters in your most flattering neckline be it crew or V-neck; a cardigan for winter or chilly nights in the summer (cardigan is a MUST!); a swimsuit that fits well and is flattering; a go-with-everything blazer (black or navy); a warm classic winter coat; a good-looking handbag; two pairs of shoes -- a comfy flat and a classic pump.
Check out some of these stores: RW&CO. (this store is a must! Even if you have no idea what to buy or what type of clothes you want to buy, this store will get you going. Plus, they have decent prices and amazing sales.), Le chateau, Rietman's (this one is a really good one too!), Suzy, and Twigland Fashions.
Ann Taylor, Chico's, Talbots and Coldwater Creek are good for the professional wear.
If you are looking for more visual ideas, check some of these links out:
5ft 8 and slim? What's wrong with short skirts? Some guys think 42 an ideal age for a woman to be most a woman, and you might also give it thought, as most woman are reputed to reach their sexual peak at this approximate age. Why should the kids have all the fun?
i'm the same way, 5'8 and slim with blond hair except I'm 16, not 42, try going with a classy fashionable look, if you want to be fancy, wear some cute pumps, a knee length skirt with a matching blouse, you want to be comfy, wear maybe a tracksuit with a color that compliments your skin and some nice tennis shoes or pretty flip flops, you don't want to wear stuff that us teens would wear like converse and short skirts, you're a woman now, but you don't want to wear grandma clothes that just cover you up. hope this helps. may I suggest where my mom shops, Cold Water Creek, Talbots, or Ann Taylor.