It is very important to have a travel insurance as this will help you in case something happened during your trip like flight delay, stolen items, sickness etc. In order to have the best travel insurance, you can either ask your travel agency if they are offering one and study the benefits they offer and the exclusions under the policy. Or you can do your own research and ask the customer service what would be best for you. Always understand first the terms and conditions before signing in in order to avoid complications during the claims process.

The guidelines would be that are indeed traveling somewhere and have trip costs that you want to insure in case you can't go or the travel company (airline, cruise line, etc...) defaults.
Then you buy travel insurance.