Slim skirts to below-the-knee length are the most versatile, as they can be styled to 30s, 40s and 50s looks. A-line styles are great for 40s outfits, and of course the full swing skirt epitomises the 1950s. Look for on-the-waist or high waisted styles. In pencil skirts, kick pleats are more 'vintage' than a walking split.
Modern skirts usually aren't long enough to look authentically vintage (unless you're going for an early-mid 60s look); try shopping in the 'tall' section or choosing the 'long' cut for a couple of extra inches.
The timeline below briefly illustrates dominant skirt styles and lengths from the 1930s to early 60s (for more examples from each period see my 20th Century Fashion Eras post; to save space I've omitted the 1950s pencil skirt and early 60s full skirt styles). In the early-mid 30s, skirts were cut long (around mid-calf), slim and with a gentle flare. Later in the 30s hemlines rose to a few inches below the knee, and became more flared. Fabric restrictions in the early 1940s brought hems even higher, to around knee-length, in an A-line silhouette. Christian Dior's New Look in the late 40s abruptly took skirt lengths down to mid-calf, in a full A-line shape. During the 1950s skirts got both fuller and narrower, giving us the pencil and circle skirt; meanwhile hemlines gradually rose, until eventually the mini emerged in the late 60s.
Trousers and Jeans
Unfortunately, on-the-waist trousers seem to be a dying breed; all modern trousers seem to be designed to divide you horizontally across the widest part of your body. Um, no thanks.
Palazzo pants are among the exceptions; they're around all over the place at the moment, and can be styled in a 1930s way to great effect.
Vintage-looking modern jeans are basically impossible to find without going down the route of vintage repro (which can be on the pricey side), but some high-waisted 1980s styles could pass for 1950s if you style them right. Most ladies jeans in the 1940s and 50s featured a side zipper, but front fly closures have been around since the mid-fifties.
Note the dark denim, tapered leg (1940s jeans tended to be cut more straight in the leg than these late 50s styles), and turn-ups.
Next in the series: Blouses & Sweaters