Lay your most-apt-to-wrinkle garment on a table or bed. Smooth out all the wrinkles. Gently lay your next-most-apt-to-wrinkle garment directly on top of it and gently remove any wrinkles. Continue doing this until you have everything in one pile (the top garment should be a sweatter, or jeans, or something like that). Fold the sleeves, legs, whatever, up over the bundle. Put the entire thing in your suitcase and pack under things, night clothes, etc. around it. The bundle is ungainly, but I've never had wrinkles. Unpack and fluff as soon as possible.
If you can, put the bundle in a clear plastic bag to expidite any necessary searches. I use a heavy,plastic,clear bag that I bought a blanket in years ago. Do not put anything hard or metal in the center and they usually leave the bundle unmolested.
Always put ANYTHING liquid in ziplock bags. Hang clothes in the bathroom when you take a shower if you feel they need steaming. Keep valuables and medications with you at all times.