Also be sure to insure your checked items, especially for an international flight. The reimbursement for lost or damaged baggage is minimal.

From the UA website:

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International
For international travels, including the domestic portions, subject to the Warsaw Convention, the liability limit for delay, damage or loss is approximately $9.07 per pound ($20.00 per kg) for checked baggage and approximately $400 per passenger for unchecked baggage. Where the Montreal Convention applies, the liability of the UA Carrier for the delay, damage or loss to checked and unchecked baggage is limited to 1,000 Special Drawing Rights per passenger.

United is not liable for damage to fragile items, spoilage of perishables, loss/damage/delay of money, jewelry, cameras, electronic/video/photographic equipment, computer equipment, heirlooms, antiques, artwork, silverware, precious metals, negotiable papers/securities, commercial effects, valuable papers, or other irreplaceable items and/or any item where a liability release was signed by the passenger.>>