Bring clothes that can be layered and can serve multi-purposes. I have a black linen dress with a matching shirt that is kind of a "jacket". I can wear the shirt over the dress for a nicer outfit for dinner, as well as using it for a bathing suit coverup.
Pick one color scheme and make sure all clothes mix and match.
You won't need more than one pair of long pants, and a light jacket or sweatshirt.
Try to pack lighter clothes. In other words if I'm going someplace in the winter instead of a bulky wool or acrylic sweater I'll pack a slim cashmere sweater. Takes 1/3 the space.
Don't bring too many shoes. I bring a pair of sandals, maybe two slim pair (hope that makes sense), plus wear either sneakers or shoes on the plane. You don't need water shoes, sandals, flip flops, shoes, boots, sneakers, and loafers.
Bring travel sizes of all toiletries where practical. I wait until there is about a week of toothpaste left in the tube and stick it away and start a fresh one for home, and then use the almost empty one on the trip. I generally do NOT suggest going out and buting a bunch of trial size things, just be creative, and leave at home the things you do'nt absolutely need.
Lay it all out on the bed before you pack it, put away anything you're bringing "just in case".
Anne