Checking if they are real first of all 
Take advice of my friends in the crypto-world, looking for ratings, for example here: https://forico.io/agencies
Take advice of my friends in the crypto-world, looking for ratings, for example here: https://forico.io/agencies
Thanks =) Maybe you have any other aspects at which you take a look?
I ask them about their previous cases, who are they are partners, for how ling they work on the market, who is in the team