I spend a few days a week working at coffee shops, which is pretty common in San Francisco, and I’ve seen some serious audacity in the last few years.

There’s always the guy communing with his computer at a table meant for four. He inevitably plugged in to the only outlet five hours ago; about the time he purchased his coffee, which has long since gone cold. Occasionally he rises to aim banter at the irritated barista, and then returns to his seat without making a purchase. Smashing.

I once saw someone pull a screwdriver out of his bag to remove a cover plate the owner had secured over an outlet. I had to restrain myself from walking over to smack his hands away.

By supplying Internet access, coffee shop owners know they’ll attract customers who want to work, but there are limits. Let’s review them:

1. Remember you’re frequenting a business. If the coffee shop isn’t profitable, it closes, leaving you pantsless in front of a Top Chef marathon. You, my friend, are a customer — so rise to the challenge. While you’re working, keep a purchase in front of you, and buy something every hour or so. If you can’t afford that, the library beckons.

2. Don’t bring a picnic. This should go without saying, but you may not bring food or drink to a place that sells things to eat and drink. Not even if you bought a coffee at some point. You can leave and come back if you want, but go eat your PBJ somewhere else.

3. Hang up. The barista is not a vending machine. Put away your cell phone while you’re ordering.

4. Tip well. Tip at least a buck every time you make a purchase. This promotes goodwill and serves as karmic rent. It’s an acknowledgement that you’re using space someone else could fill. Someone who tips.

5. Clean up after yourself. If you spill half the creamer on the counter before you find your cup, wipe it up. Empty sugar packets go in the trash, which is conveniently located inches from your hand. Bus your table between purchases and clear the table before you go. If someone takes your empty glass while you’re still sitting, that’s a forceful hint that it’s time to buy something else or leave.

6. Let the baristas be. If they want to talk to you, they will, and a pleasant conversation may ensue. But if you feel chatty — or god forbid flirtatious — direct those impulses elsewhere. Employees can’t be rude in the face of your attentions, and they can’t exactly leave work to avoid you.

7. Take one chair, and the smallest table available. If that happens to be a large table, offer to share until someone accepts. Don’t wait for others to ask, and don’t cover the table surface with papers in hopes that no one will bother you. As soon as a smaller table opens up, move.

8. Leave chairs free. If the space is busy, your bag goes on the floor, not a nearby chair. That way other people can use the chair without interrupting you. If you’d like someone to clear a laptop bag so you can sit, say, “Excuse me, is someone sitting here?”

9. Don’t bogart bandwidth. No P2P or large file downloads while everyone is sharing a network. Besides, we can all see your porn, and it’s awkward.

10. Respect the owner’s intent. If wi-fi is turned off at certain hours, then your laptop probably isn’t welcome either. Be aware of the cafe’s culture. If everyone around you is reading newspapers, or having quiet chats, this isn’t the place to start coding.

11. Avoid noise pollution. Switch your cell to vibrate, and take calls outside. If that’s not possible, keep conversations brief and quiet. Also, mute the sound on your computer, or wear headphones. Do you have any idea how much time you’re spending on Hulu?

12. Recognize that everyone wants the outlet seat. Unless outlets are plentiful, don’t use one unless you must. Arrive with a charged machine, and consider bringing an extra battery to avoid the whole drama. If you’re sitting at an outlet and you have enough battery to work for an hour or so, offer to share.

13. Don’t tamper with outlets. If an outlet is covered with a plate or tape, are you seriously willing to be the guy who opens it up? Don’t be that guy. What’s more, if there’s a fan, a lamp, or any other electrical device plugged in, you may not unplug it in order to charge your machine.

14. Ask before you pull out a power strip. In some cases it’s fine to bring along a power strip to multiply outlets, in other cases it irritates the owner. It’s more likely to be a good idea at a Starbucks than a mom-and-pop cafe. Another good sign is if the coffee shop has several available outlets, and is clearly set up for laptop use. When in doubt, ask the owner.

15. Once in a while, change your scenery. If you plan to spend an entire nine-to-five workweek in the same space, you might as well get a real job. Perhaps you’d be interested in learning to make a good latte?

The day may come that you’re too engrossed in your work to notice that you’re doing something rude. Hopefully, that situation will be such an anomaly that everyone will cut you some slack.

Now let’s go get some coffee. You can sit with me.