Here is the second installment of Coffee Shop Commandments you need to be aware of if you are to visit a coffee shop at any point in the future.
Thou shalt not play your guitar Just because there are open mic nights at this establishment, it is not an indicator of this being a constant testing ground for your new song or whatever cover song you're working on right now. All these people are NOT here to hear you play. Leave your guitar at home. (Your song isn't that great anyway. I'm sorry...I'm a friend)
Thou shalt not drink of the outside Why is this commandment necessary? Honestly, this is a business and though their competitors' ads may be accepted, their competitors' PRODUCT is not. You may not bring another company's coffee into this shop. It is not rude for them to ask you throw it away; you are rude for having brought it in.
Thou shalt not make this your marriage bed You would be offended if I sat next to or in front of you with a bucket of popcorn and a video camera while you and your significant other make out on the coffee shop couch, but I cannot understand why you're offended. You quite obviously wanted your affection to be a spectator sport or you wouldn't have chosen to do so in a public coffee shop. You are gross!
You shall talk to others Yes, we all have work to do. That is why many of us are here, but don't be afraid to speak with others. If you come here all the time, there is no reason we should not know one another. If you are here all the time, you should know the baristas' names. You should start to recognize the others who are here all the time...engage with the community you are observing.