I do a lot of leisure travel. I routinely utilize many of the suggestions posted above. Here are some more of my own:
Never pack more than you can physically carry. Period.
I agree that there are very few destinations in which denim jeans are both appropriate and convenient. As a female, I find that two pairs of khaki slacks - or khaki and casual black - work much better. They're lighter weight, and lots more versatile. Wear them with a T-shirt and comfy ankle boots to any casual event, and dress them up with a simple black blazer for dressier venues.
If my destination is a hotel or a series of hotels, I will log on to each hotel web site before my trip to verify amenities. Most all these days, even the budget hotels, will at least have shampoo, soap, and a hair dryer. I leave those things at home. If my hotel doesn't have in-room coffee and it's a short enough trip to have plenty of room in my bag, I have a plastic Betty Crocker 4-cup percolater coffeepot that I take along. In the pot I pack baggies of coffee, nondairy creamer, sugar, and a plastic spoon. I add a little plastic mug that's lightweight and unbreakable.
I usually bring home more toiletries than I take, as I collect the freebies given to me in the hotel. I then take them with me when I visit destinations that don't offer them, such as renting a condo or camping. I use them there, and don't have to worry about bringing them home. And the fancier ones, such as the Green Tea that Wyndham gives, can make nice stocking stuffers.
When traveling internationally, I pack all black and neutral colors. Everything can be worn with everything else, mix-and-match. No worries about being accused of wearing the same outfit every day. The most amount of clothing I ever pack is about 4-5 days' worth, even if I'm going to be gone a week or more. And I pack a small but adequate bottle of Woolite. I wash everything in the bathtub or the sink and it's ready to go.
If I'm going to a destination that doesn't offer an iron and ironing board, I don't take a travel iron. I've found that a small hand steamer works much better - I can steam out wrinkles while my clothes are on the hanger, and not have to worry about scorching a dresser top or burning my clothing due to a lack of steam. And a hand steamer is a lot lighter to pack too.
I also take along magazines and paperbacks that I can leave when I'm done with them.
I always take a swimsuit. It takes up very little space and can be a godsend. Admit it - how many times have you arrived at your destination and longingly gazed at the pool or ocean but couldn't go in? It's always worth having, "just in case."
Hope these help...
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