How good of you to patronise a proper coffee bar. But do you know the rules? Better question — do you follow them?
Here they are, in no particular order.
Be friendly. Even if you are tired, or angry, or whatever it is. You are in public. Behave.
Tip well. Keep in mind that if the coffee and the service were genuinely poor, that part is up to you. Otherwise, tip.
Do not be gross at the condiment counter. Bin your rubbish. Wipe the small spills. It takes four seconds and the person who would otherwise do it is busy.
Ask questions. The people behind the bar are working hard to represent the company standing behind them and the product they are serving. Chances are they would love to talk about both, and almost nobody asks.
If you are camping, keep buying things. Using the wifi for four hours, occupying a table, or both — that is fine, that is what the room is for. But it is how the business survives, so buy something occasionally.
Do not be gross in the bathroom. We should not have to write this one down. We have written it down.
Enjoy yourself. This is supposed to be pleasant. That is the entire reason the place exists.
Keep enjoying yourself.
All of this is fairly common sense and fairly universal, so feel free to apply it elsewhere in your otherwise excellent life.