Do I go to my car for my ID since I don't take it into my appointment?

If so, then they run my plates but all that is OK if I say nothing like you said, right? And of course I've done nothing.

Or should I take ID into my appointment?

You did a good job explaning everything, I would just add one more thing to say is "Am I free to leave".  If they say "yes", then beat feet!

The police have a right to ask for your ID. You do not have to give it, but that is likely to involve additional questioning.  If police ask why you are at a particular location, answer: "it was a confidential appointment".  If they ask with who, answer "I would be committing a contractual breach by answering that question."

If they ask for further information, respond that the legal issues are complex and you'll need to consult with your attorney prior to answering.  If the cop on the beat wishes to pursue, you are likely screwed.  With no probable cause, their inquiry is likely to go nowhere

...make sure you have the ability. No ID, no name, "I'm I free to go?" Silence unless you are asking if you are free to go. They can try to wait you out, so be patient and silent. Take a nap or pretend to. Do not go to your car if you have one. A nice walk or coffee shop works out well.

Give them your real name.  Anything else you invoke your 5th Amendment rights.  Don't try to outsmart them; they are trained to get information out of people.  Your best chance of walking away is not giving them any more information than they already have.

You are only required to provide an ID if you're operating a motor vehicle.  Any other time you are under no obligation to provide an ID and are not violating any laws to not provide an ID.

However, if they ask you your name you are supposed to provide them your real name.  Being untruthful could land you in trouble.

What you want to say is, "Officer am I being detained or am I free to go?"  They can detain you in order to try and get you to say something to incriminate yourself.  They have to have reasonable cause to detain you.   But they can't detain you forever.  Your job is to find out if you're arrested or not.  So just keep your mouth shut.

Be advised;
 the P don't just lie to you, they lie to the court also.  anything you say will be used and twisted and edited and misquoted.  The vice police are more dishonest then con men.  I have seen cases where police will plant evidence, empty condom packages ect...  This is their game on their court, if you play you will lose.

"I have nothing to say.  I need to talk to my lawyer, am I free to go"  repeat it again until they give up.  If you look right at the cop and politely repeat those words they will accept that you are too smart to entrap yourself.  Nothing else you can say could possibly help.  Learn the script.
name, rank, serial number.  

be safe everyone

If you are in the hobby you need to know the rules. You will not talk your way out of it. If they had enough to arrest you they would have already done it. It is amazing watching the reality show The First 48. Most people end up talking to the police during an "interview" the police let them dig a hole then they catch them in lies, use tricks and lies to get them to change their story and get trapped.  The next thing they know they are confessing to a murder the cops could not have proved if they had just shut up and asked for a lawyer.  

Learn about a terry stop vs. an arrest.  

If stopped do not discuss why you are there.  Give your name or ID if asked, ask if you are being detained, ask if you are free to go.  The can detain you while they investigate.  It is imperative to decline to answer all questions besides name. Keep your mouth shut even about little details time, place who, why etc.  You do not have to feel you are being impolite. You can say I would be happy to cooperate and that your lawyer handles any and all questions related to police matters.  At that point they will either investigate further, arrest or cut you loose.  Don't go to a car, just go for a walk.  

Good luck and shut up

A few things come to mind...

1.  In MINNESOTA, you usually do not have to present an ID, unless you are doing something that requires an ID.  For instance, if you are driving, drinking at a bar, carrying a permitted concealed weapon, etc. you absolutely must present your ID upon request with or without probable cause.  In all other cases in MN, you are not required to have ID, nor show it even if you do.

2.  There is a difference between a Terry stop (named for the supreme court ruling Terry v. Ohio) and being formally detained.  For instance, if you are walking down the sidewalk and they say "hang on a minute, we'd like to talk to you" you can't just refuse even if they don't have probable cause.  You do HAVE to stop.  In many states you DO have to verbally state your real name, and in some states your address during a Terry stop.  That is, you have to honestly identify yourself even if they don't have probable cause.

3.  I capitalize MINNESOTA for a reason...  ID laws are state laws and MNs are different than Iowa, Wisconsin, etc.  Don't ever refuse to to identify yourself or show your ID unless you are SURE the state you are in allows you to refuse.  Many states don't.

4.  You can withhold consent in a way that doesn't get your ass beat with a baton.  If they ask for consent to search, answering "kiss my ass" is not at all the same as "Sir, if forced to comply I will not resist or threaten you in any way, but, I will not consent to a search."

5.  Remember what a Terry stop is...  It specifically means "we don't have enough information to really detain you, but we're allowed to ask you a few questions to help us understand what's going on here."  You aren't required to answer, but they are allowed to ask.   If they already had enough evidence to arrest you, believe me, they'd arrest you.  So the fact that they need your help in proving your guilt should tell you something

As other have said, police can and will lie to you to eek out a confession.    

They can also detain you for 72 hours without charging you, some states it is 48 hours, after which they must either release you or charge you with a crime

Some times chiefs sleep with our women...sometimes they really go rogue and rob banks.  Banks are the real criminals BTW...I love it when pigs get called out in public.  Clap clap clap New Ulm...

To the OP, it's a misdemeanor to provide a false name to the police. It's also a misdemeanor to lie to the police. A creative officer can even charge you with obstruction of justice depending on the circumstances, which is a felony.... This is why it's best not to speak to law enforcement or answer any questions without a lawyer present. If you are being charged with a crime, then you ARE legally required to ID yourself, but you're NOT required to answer any questions pertaining to your alleged crime.

Talking to the police can NEVER, and I mean NEVER help your case.... As the saying goes, "You can beat the rap, but you cannot beat the ride." ... Keep your mouth shut, and it greatly increases your chances of beating "the rap".

NOW, if you're loitering around a high drug and/or prostitution area, that could give them the aforementioned reasonable suspicion they need to obtain your ID. When approached by the police and questioned, the best question you could ask them is, "Am I being detained or am I free to go?". If they say something like, "I'm not detaining you, I just have a few questions" or "I just want to talk to you man." ... You should say something along the lines of, "I don't have time to chat, have a good day officer." (Casually walk away, NEVER run, running can give them reasonable suspicion that you've broken the law or that you're about to do so).  

If you're walking away from them, at that point they'll either let you go, or tell you that you're being detained. You 'could' ask why, but at this point it's best to tell that you won't be answering any questions and that you'd like to speak with a lawyer.... They may say, "You're not under arrest, we just have a few question since this is a high drug and/or prostitution area."  

Their tone will usually be calm and friendly at this point, like they're your buddy... Don't be fooled, they're trying to nail your ass to the wall. Simply reiterate to them that you won't be answering any questions, and ask are you free to go. If they continue to question you (which they probably will), you can just look at them (it may be awkward for you, but it's awkward for them as well.) Or you can repeat your previous question, "Am I being detained, or am I free to go?" Remember, you may have to repeat this a few times as they most likely will keep trying to ask you questions and extract information from you. Remain silent, ask if you're free to go, or ask for a lawyer.... Those are your ONLY three options, don't try and talk your way out of it no matter how smart you think you are. Police can AND WILL twist what you say, and at times outright lie about what took place.  

Minnesota is a one party state, which means only one person has to consent to recording a conversation. This means you can (and should) record any conversation and or interaction with police if you have the opportunity to do so. Wearing a body camera isn't a bad idea, as you won't have to go reaching for your phone (and possible get shot) when the police approach you.

They may place you under arrest, they may not. At the end of the day, if you do end up getting arrested, it's better to be going to jail without having incriminated yourself, then to have ratted yourself out by saying too much.... Remember, NEVER talk to the police without a lawyer present, NEVER answer ANY questions.

***DISCLAIMER: THE ABOVE INFORMATION IS NOT MEANT TO BE LEGAL ADVICE AND IS GENERAL INFORMATION THAT CAN BE FOUND BY PERFORMING A SIMPLE GOOGLE SEARCH ABOUT KNOWING YOUR RIGHTS.***