Age dependent. The answer depends considerably on the infants age but in general protect your baby from electrical outlets, stairs, small particles on the floor, and from falls.
Porta-crib/playpen. Curious toddlers and mobile infants present a challenge to their parents when traveling. Using a portable crib as a playpen can help. Some parents bring along baby proofing supplies (electrical plugs/door knob covers/toilet latches, etc) many hotels will lock the in-room refrigerators for you. Watch for pinched fingers with drawers and doors. Moving furniture can block access to problem areas.
Inspect the room. When traveling with a baby or young child, the parents should inspect the hotel room carefully, looking behind the curtains, under the bed, etc . . .. Windows and doors should not be openable by a baby or young child. One parent should always be with the child. Be extra careful about water, as kids can drown in toilets or bathtubs.