I met a (architecture) contractor in the QQ group. We talked well in the group. I planned to go to his construction site to see.

What should I pay attention to when I go to the construction site and seize those favorable evidence (such as asking him to sign a contract with me, knowing Party A's company, etc.)? (I am afraid of being cheated, and I have evidence to speak) Trouble you. Satisfied, I will add points