Short answer
Verification should focus on relevant facts and use trustworthy sources rather than invasive searches or public gossip.
Islamic Guidance
What Islam teaches
Islam encourages verification of important information while prohibiting spying and backbiting.
Practical Guidance
What you can consider
Verify identity, marital status and important claims proportionately. Ask direct questions and use trusted references instead of trying to uncover every private detail.
Sources
Qur'an 49:6; Qur'an 49:12.