If you are engaging the services of consultants or volunteers, or hiring someone into your team - and you are looking to confirm their Salesforce skills - this is what you should be looking for.
1. Ask for the link to their Trailhead Profile. Its should be a URL that starts with trailblazer.me/id/......
2. Certifications appear just under the profile summary - look for the green active dot next to each certification. Certifications expire if they are not maintained.
3. Do not let anyone touch your org without at least Salesforce Admin Certification. This gives them GOD-LIKE power to all your data. I would be asking them to sign an NDA also. Make sure you reference check them properly!
4. If you are using the NPSP (Non Profit Success Pack) then hire someone with NPSP Consultant certification - it's very important that they understand all the unique features and benefits.
5. Check their Trailhead badges tally - this shows their commitment to learning and the breadth of their knowledge.
6. Check how many Superbadges they have. Superbadges apply skills to complex, real-world business problems. These prove a person's expertise in specific roles.