Bed bugs do not arrive through the window. They travel: in a suitcase after a trip, inside a second-hand wardrobe, in a visitor's overnight bag. Catching them at the door is a two-minute inspection. Treating an established infestation is two visits and a fortnight of laundry.
In a hotel room
Put your luggage in the bathroom first — tiled floors offer bed bugs nowhere to hide. Then pull back the bed sheet and run a card or your fingernail along the mattress seams, especially at the corners and the head end. You are looking for live insects the size of an apple seed, pale shed skins, and small dark spots of digested blood on the fabric.
Check the headboard and the bedside furniture too: behind the headboard where it meets the wall, inside drawer joints, along the screw holes of the bed frame. If you find signs, ask for a room in a different part of the building — not next door, where the same infestation often extends.
Second-hand furniture
Second-hand furniture deserves the same treatment before it crosses your threshold. Run a torch along every seam, joint and screw hole. Wooden and fabric furniture carries the risk; solid metal and plastic rarely do. If in doubt, leave the piece in the sun for a day and inspect again.
Coming home from a trip
When you come home from a trip, unpack in one place, hot-wash what you can, and vacuum the empty suitcase before storing it. If bites or blood spots on sheets appear in the weeks after travel, inspect the mattress seams immediately — early treatment is a small job, and it never gets smaller by waiting.