Check that the event is actually happening. This may seem a little elementary but people have bought tickets to concerts that were never scheduled to take place.
A brief browse on the official website of the arena where the event is set to happen will reveal if the event is actually taking place or not. While you are on the official website make a note of the telephone number for later use.
Make sure that the telephone number on the ticket matches with the telephone number taken from the official website. If it does not match then it does not necessarily mean that the tickets are not real but you should ring the number on your ticket and find out why the number is different. It could possibly be that the numbers direct you to different departments of the same company. Ask for clarification about this from the assistant on the phone.
Ask the assistant on the phone if your seat numbers are genuine. The assistant will ask for the name on the ticket along with the row and seat number. Knowing that many people buy tickets on their own credit card for somebody else the assistant will not necessarily expect your name to be the one on the ticket. The assistant will find out and tell you if the details on your ticket are accurate.
Purchase tickets directly from the vendor; then you can be confident that your tickets are authentic. However, if you have purchased them from a third party, an individual or a ticket broker, there is one more necessity before you can be sure that they are not counterfeit. Contact the third party from where you bought the tickets and ask for a proof of purchase. That should include their name and the last four digits of the card they bought the tickets with, if they did indeed use a card.
Recognize that the event exists and the details on the ticket are correct. With the original proof of purchase you can now be confident in the knowledge that you have done everything required to ensure that your tickets are not counterfeits.