Customs Q re EU/London/Copenhagen trip - how many times thru customs?

Are you stopping for a day or two? Are you checking luggage? If you are stopping in the UK, you will have to pass immigration and get your passport stamped then collect your luggage off the belt then walk out the door marked "Nothing to Declare" (if that is the case). When you leave the UK, you will get an exit stamp on your passport. If you are just changing planes, you may or may not need to go through immigration, but your bags should be checked through to your final destination where you go through customs.
If are just changing planes in Copenhagen, you will pass immigration and get a passport stamp, then continue to your destination where you pass through that "NtD" door again after you've picked up your bags. If you are stopping in Copenhagen, well you know the drill.
Advice on going through immigration in the UK? Just get in the right line and be patient.

First of all, there is customs (control of goods), passport control/immigration (control of people) and security. These are three different things, and easy to confuse.

Second, exactly what you go through where and when is determined by your EXACT itinerary. "EU countries" isn't specific enough. The big distinction is Schengen vs. non-Schengen countries. Schengen countries have agreed to abolish routine border checks (but still can have these). Switzerland and Norway are not EU, but are Schengen; England and Ireland are not Schengen, but are EU.

Third, the reason Schengen status is more important than EU status is because in Europe, it's passport control that can take time. In most cases, customs is just a matter of walking through the "Green Channel - Nothing to Declare" line. It's not like the US, where everyone has to fill out forms and personally have to hand the forms to a customs agent. Of course, security can take time as well, and that can occur whether or not you have customs or passport control - it depends, again, on exactly what airports and terminals you are using for that connection.

For most itineraries, you go through customs at your final destination. If you are ending in a Schengen country, you go through passport control at your first Schengen airport. For instance, if you fly from the US through Copenhagen to Rome, you would go through passport control in Copenhagen (may be quick or slow), and customs in Rome (again, this is just a walkthrough). With your itinerary, it's more complicated.

Fourth, if you have to go through customs, immigration, and/or security, it's not optional. You just follow the crowds. As said above, bring a good supply of patience, particularly if you arrive at a busy time.

If you're changing planes in London Heathrow, their website has an excellent tool to show you exactly what's involved. Just go to this link and put in all the relevant information: http://www.heathrowairport.com/heathrow-airport-guide/flight-connections/connection-guides

If you need more information, post your exact itinerary, so others can help.

Not sure why you have separated out 'England' and Denmark from others in the EU as there are no routine customs between any EU country, although there are limits on some goods for personal user, such as cigarettes.

If you really meant immigration then it would depend on exactly which countries you are visiting, and in what order how many points you would pass.

Thanks, all.

Wow, that's a lot of info. Thanks, especially, Harold, for taking the time to lay it all out. I've traveled in Europe before, but always by train once I arrived. This time it's lots of flying. So...I am spending a few days in each of these stops, in this order:
From Seattle via Detroit (3-hr layover) into Amsterdam (Schiphol), thence to London (arrive Southend, leave Sansted), thence to Copenhagen (in & out of main airport), thence to Venice (in & out of Marco Polo), thence to Paris (into Orly), and home from Paris (out of CDG), but with an overnight layover in Minneapolis. Oh, and all with carry-on bag only.

As I'm writing this reply, I can't see all your detail, and I will review it more carefully, but it sounds like I should just plan on a combination of (1) having nothing to declare when possible, (2) following the rest of the travelers, (3) asking along the way and, (4) inevitably looking like a clueless tourist. Is arriving 2 hours ahead a good rule of thumb for EasyJet and AirOne?

Thanks for your details.

"From Seattle via Detroit (3-hr layover) into Amsterdam (Schiphol)"

In Seattle, you should get boarding passes for both your SEA-DTW and your DTW-AMS flights. You will probably pass through security in Detroit (I don't know that airport at all), but otherwise you will proceed directly to your next flight. In Amsterdam, you will go through passport control and customs (again, just a walk through).

"thence to London (arrive Southend, leave Sansted)"

From Amsterdam to London, there will be passport control (you're going from Schengen to non-Schengen). Your departure airport is Stansted (two t's).

"thence to Copenhagen (in & out of main airport)"

Again, you're going from non-Schengen to Schengen, so there will be passport control.

"thence to Venice (in & out of Marco Polo), thence to Paris (into Orly)"

From Copenhagen to Venice and Venice to Paris, it's like a domestic flight in the US. You will need your passport as your ID, but there will not be any routine immigration or customs checks.

"and home from Paris (out of CDG), but with an overnight layover in Minneapolis."

You will go through passport control leaving CDG; get there three hours before your flight just to be safe, as the airport is huge and always crowded. If you are getting any VAT refunds, allow even more time. In Minneapolis, you will go through passport control, then customs.

"it sounds like I should just plan on a combination of (1) having nothing to declare when possible, (2) following the rest of the travelers, (3) asking along the way and, (4) inevitably looking like a clueless tourist."

(1) Since all of your travel within Europe is within the EU, you shouldn't have any customs checks while in Europe, so there's no worry about declaring stuff (when you come home it's a different story, depending on what you're bringing). (2) Since you're not actually changing planes in Europe, when you get off the plane you just follow the signs to ground transportation (with carry-on only, you won't need to go to baggage claim). (3) Asking along the way is very important if you're at all lost or confused; don't waste any time. (In Milan, I met travelers who had been looking for their check-in desk for an HOUR, because they hadn't asked when they first had difficulty). (4) There's no need to look clueless; all airports have English signage.

"Is arriving 2 hours ahead a good rule of thumb for EasyJet and AirOne?"

Check the airline websites for their own recommendations. In general, you don't need to get to the airport so early for intra-European flights, but you don't want to miss any cutoffs and be denied boarding.

Do on-line checkin whenever possible, as it speeds things up (even if you can't print your boarding pass). For Easyjet, I think you have to print your boarding pass before you get to the airport, or it costs extra (again, read their fine print carefully; they make money by enforcing all their rules).

Again, huge thanks, it is so reassuring to head out with lots of information, and it's so clearly laid out - thank you thank you! I will be sure to check re boarding passes etc on EasyJet & AirOne.

I will add an in-expert observation based on flying 2weeks ago SEA-> AMS, AMS -> DUB. I thought we would go thru a passport control in AMS but we did not. There was a security screening to get to our gate, but nothing else until Dublin where we did both passport entry and customs walk-through.

That would have been a connection between 2 non Schengen countries.