If you're worried about looking like a dork abroad, know that not dressing appropriately in a conservative country is worse than looking silly, you'll also be acting like a jerk. I'm talking about most of Southeast Asia, the South Pacific, Asia, Morocco, Tunisia, small villages in Central and South America and more - in other words, those parts of the world that maintain a modest dress code without requiring something more hardcore like a burqa.
Figuring out what to wear while maintaining some style dignity can be hard for travelers, especially women, who have to cover up much more than men and who are more closely scrutinized. The question is, how does one dress conservatively, look a little nice and avoid overheating at the same time? After over 20 years of travel in these parts of the world and looking pretty awful through most of it, I've finally acquired a few key pieces that I feel keep the balance between comfort, appropriateness and fashion.
Here are my top 5 essentials:
The peasant top
Try to find one in a feather-weight, crinkly cotton that's not too see-through. Three quarter sleeves are best and make sure if there's a tie at the neck the keyhole part doesn't show any cleavage. Avoid mid-weight or heavy fabrics and any tight elastic. Think, breathable and keep it simple without a lot of flamboyant embroidery or other standout features.
Here's a current favorite of mine from Old Navy.
A good cut here is key. I hate boxy shirts that add a few pounds to my look but too tight is a no-no. I go for the lightest cotton possible that's still opaque, sleeves that are longer than a cap sleeve but shorter than three-quarters and loose enough to breath. Also make sure it's long enough that you're not going to bare any waistline when bending over etc. I personally like a mellow-colored print like ikat or tie-dye stripes to hide stains.
If these go out of fashion again I may die. Mid-calf in a lightweight sturdy fabric is a must. A drawstring waist is another plus since you'll be able to adjust them so they'll stay up properly without a belt through all the stretching and washings and un-washings they will surely go through - as well as any waistline changes travel may bring to your midriff. I have a pair right now that are my all-time favorite: they have good button cargo pockets and are made of a fabric that looks like cotton but is actually a 100% silk weave that's cool, soft and sturdy. Go for dark colors. I like fairly low-waisted styles because these look better on me, but if you can pull off the "natural waist" look without looking like you were on a $2 budget at Goodwill or got a bitchin' Christmas gift from your grandmother from Royal Robbins, then go for it.
Here are my favorite capris from Hei Hei but unfortunately they don't make them anymore.
Mid-calf length skirt
I actually don't pack these anymore since I find they're not practical for anything remotely active but if you're going to be hanging out in a city a lot or plan on needing to dress nicely at night, this can be an essential. Again, find a lightweight fabric that won't need ironing and don't get a skirt so full that it may get blown up by wind and give the conservative world a peek at your underpants. Length should be mid-calf.
In general, I only wear long pants for insect protection, cold or because they're the only clean thing I have left to wear. I also wear them on the plane so they need to be stretchy enough to sleep in and look nice enough that if by some miracle of fate I get upgraded, I won't look too sloppy to sit in business class. I like light, soft cotton or Tencel with something elastic-like in the waist that won't pinch or stretch. Again, I think "natural waist" is a sin, but that's a matter of taste. Straight leg works best; anything with a flared leg will get caught in stuff and provide a tunnel for bugs to crawl up and skinny pants will be too sexy and cling to your humid skin like soggy plastic wrap. Go for dark colored. I'm partial to slate grey.
Bonus Piece: Silk scarf
Find the biggest one you can find that can compress into the smallest folded square. I keep one in my purse at all times on the road in case I need extra arm coverage or something over my hair for religious temples or particularly conservative places. It also can be used as a real scarf to add a little flair to your outfit (think: business class) and can provide warmth in unexpected air-con disaster areas like buses and cinemas.