Here are tips to ensure your claim is not rejected:

1. Don’t suppress vital information: Insurer fixes the premium based on the information provided by you which includes your age, occupation, liquor/tobacco intake, pre-existing diseases, family history, details of other policies that you hold etc. It is a mistake to conceal facts in order to lower the premium amount as it can backfire. Disclosure and reporting of facts are entirely the responsibility of the insured; therefore, ‘do not’ conceal any material facts while taking life insurance.
2. Don’t avoid medical tests: Although most of the insurers demand a compulsory medical test to be done before approving the proposal, however there are few who waive-off this condition. It is always in the best interest of the insured to have his/ her medical test done to rule out the possibility of having pre-existing disease as a rejection reason.
3. Fill-up the form yourself: Most people entrust their agents or advisors with the work of filling up the form without realizing that a single omission of a fact can jeopardize their insurance plans. This can be easily managed if you sit with your agent (or online) and fill up the form yourself as chances of missing out any fact are lessened and you would also be assured that you have complied with all rules. It is also advisable to keep a copy of the filled form with yourself.
4. Don’t let the policy lapse: Claims can be settled only when the policy is active. So, it’s important to put a reminder for yourself of the premium payment due dates. Forgetting to pay the premium within the grace time can result in policy lapse and the claim made even after a single day of such lapse will be rejected by the insurer.
5. Keep nomination updated: Information pertaining to the nominee is very essential as he/she will be the actual beneficiary when the claim is made. Therefore, make sure that this space is kept updated at all times. If the nominated person in an application dies before the policy holder then change the nominee in the policy immediately. Also, it is common for an unmarried man to name his parents as nominees. But, after marriage he should ideally make his wife as nominee, as there are chances that at the time of death of the insured, his parents may also be deceased.
6. Verify policy document: Finally, once you receive the policy document, verify the details mentioned therein with that provided by you. Report any mismatch/error to the insurer immediately and ensure that it gets rectified. In the event of a claim, the claimant has to provide the mandatory documents for smooth settlement of claim. The whole process, if followed unfailingly, can curtail the claim rejection possibilities to a greater extent.

In my opinion, Financial planner has an important role in structuring and executing your  Insurance Plan. So its always better to deal with a Certified Financial Planner who has experience and credibility in the market.