Travel insurance is one of the most important documents when you travel. This will be your safety net if something goes wrong. It is best to have a copy of the travel insurance policy in two separate places (one that you can bring along and one that you can leave behind) for the name of insurance company, their contact numbers and the policy number. Claiming for travel insurance differ per case.
In case of sickness, you should immediately contact the insurance company for details of the medical coverage. This will save you from getting expensive treatment which may not be covered by the insurance at the end.
In case of theft on travel items, what you need to do first is report it to the police. You can claim insurance based on evidence of theft and police report.
In case of lost items from the airline, bus or hotel, you must first let them admit culpability so you can claim insurance. Otherwise, the airline, bus or hotel may be responsible to have it found or settled.
Generally, claims require strong evidence of the case to be honoured.