It is great that in many restaurants you can bring your dog to dine with you- but there are certainly some guidelines you should follow when considering.
The top rule of thumb is that your dog really needs to be well socialized and not likely to be reactive, bark, growl or snap at people especially, but also other dogs.
It is most important that your dog be people friendly because especially in a situation like that where people are intrigued and excited by a dog in their presence. It is likely they may want to pet your dog, which while you can refuse and say he or she isn't friendly, people do not always listen- and it is not fair to others to bring a dog that really can't/ shouldn't be petted to a situation where people expect otherwise. the fact that you have brought your dog to a "people thing" subtly indicates they are capable of behaving in that situation.
This is even more true if your dog is reactive to people walking by or the busy nature of a restaurant and will not sit quietly but rather is actually endangering the welfare of others. While I stand firm on not bringing a dog that might bite if reached for to a restaurant, that's still preferable to a dog that may act erratically and could bite someone who isn't even trying to approach.
In short, if your dog is not 100% predictable and reliable with people, just don't do it.
When it comes to dogs, you must remember that other people who patron and or bring their dogs to restaurants are also hoping to enjoy their experience there- which will be spoiled by a dog that is reactive to another dog that happens to be there.
Many people have ill-fitting equipment and collars that slide over the dog's head with absolutely no effort- or the leash you tie around your chair may fail. Either way a dog that has the likely potential to not get along with other dogs, is a liability waiting to happen- as even the best dog handlers have accidents happen. You can never be 100% foolproof so don't let others pay the price if that could ever happen.
If your dog cannot sit quietly and will react to other dogs passing by or sitting within eyesight, then you shouldn't bring them.
This is even more true if your dog has behaved unpredictably in the past with other dogs or you "just don't know what sets him off"- because your dog could create a small annoyance at best- and a dog fight or injury at worst.
Even if your dog is people friendly but dog reactive, remember how easy it is for a person- especially a child- to get caught in the fray of a dog fight. They are at face level for many dogs and even if the dog may not have intended to bite a person, it happens- and could not only be a lawsuit for you, but potentially the death of your dog should it be deemed dangerous for his or her actions.
Your dog is like a loaded gun and you need to be responsible and respectful of how that affects others- remembering that even in capable hands, guns can go off accidentally and shoot someone in the foot!
In terms of other etiquette, it is critical you respect the boundaries others have for eating. Just because you can bring a dog doesn't mean people will or should tolerate behavior that is considered gross, unsanitary or rude.
A great example of a huge no would be letting your dog sit in your lap or eat/ drink from your plate/ cup. While you may share that kind of affection and lack of boundaries with your dog at home, it is in no way appropriate to expect others to eat around you while you carry on in that way.
People will at best find it "strange" or odd, but at worst may be downright disgusted, sickened or unable to eat their own food.
They will likely find it unsanitary which may reflect poorly on the restaurant and their standards as well. No one wants to wonder whether a dog slobbered all over their dishes before they were laid down on their table- even if they were washed.
That kind of negative aspersion cast on the establishment would be unfair and could also cause people to complain eventually forcing the restaurant to change their rules.
It is a privilege to bring your dog to typically human experiences so don't be the one to ruin it for others.
Another big no would be letting him or her run freely. It is absolutely a requirement that your dog be securely on a leash with a proper fitting collar or harness- and that leash needs to be in your hand or very securely tethered to something stable. You don't want your dog pulling a Marley and dragging the entire patio table down the street as her runs away!
The same would go for leaving your dog alone- you simply can't. You do not know what others will do in your absence to annoy or frighten your dog, which could elicit a bite- or what other person might not be paying attention or monitoring that dog as they pass yours.
Not only do people deserve not to be tripped by a dog darting out from under a table but leaving your dog to fend for themselves could endanger their well-being and safety. If you must go to the bathroom or step out, bring your dog with you.
Lastly, a dog that has a problem with marking is probably not a dog that would be acceptable at a restaurant, because it is pretty likely that they will try and mark on someone's feet or their jacket hanging on the back of a chair. It is absolutely unacceptable to think that anyone will be ok with being peed on while eating out- so either slap a belly band/ diaper on your dog (because females can mark too), or just don't do it.
One thing which shouldn't have to be said, but I will just for the sake of being thorough, is if your dog is feeling ill, having diarrhea or throwing up must stay home without any question!