No just turn the ignition to the first position which is where the stereo is usually wired into. Obviously make sure the stereo is off and no ignition light is showing on the dash. I have done this loads of times and never had a dead battery.

Disconnect the battery?
If you use a pull bar you will have to provide lights of some sort, check out an RV catalogue for wiring harnesses that allow you to plug in to the towed cars light's..........In RV parlance the towed car is called a Toad! I pull a Land rover Discovery behind my RV the only problem is if you need to reverse, it's almost impossible to do it without unhitching the toad first.

The photo I have is the Mini that I had while living in Italy. By turning on the switch like you said, will that drain the battery?

Hi Jeff. Funny i thought of your van when i had finished typing and thought it may be you but the avatar picture threw me off.
Pulling most trailers and or vehicles is usually not a problem it is whether the towing vehicle has the braking ability you need.
Joe pulled your Mini everywhere with a Nissan pick up and a tow bar, Rocky his good friend also uses a tow bar behind a Ford Edge. I have used a tow bar behind a 2.3 liter 4 cylinder Mazda pick up with no issues you should be fine with the 6 cylinder Honda van.
Just try it one weekend for a trial run and see if you feel ok with it.
Remember to leave the ignition in the accessory position so the column is not locked and out of gear and make sure the fuel pump switch is off.

We used to flat tow a mustang drag car, all was good with the method until one day we hit a decent bump on the freeway, and the car dropped into 2nd gear. When we got it pulled over and the smoke cleared, all was ok but we never used that method again. For a front drive mini a car dolly is good and not too expensive.

You saw my van and the tow hook up on the mini when I bought it. I remember you saying that our van could pull the Mini the day we were with you looking at in Orlando. Just wanted to see if anyone else had pulled one with a Honda Van and what their experiences were. This Jeff in NC.

The van should pull a Mini with a trailer or tow bar just fine. Look on the internet or your handbook for towing and tongue weight capacities. If you decide to use a tow bar Harbour Freight sells a sturdy tow bar set up for around $60 when it is on sale. Make sure you have 3/8" or 1/2" grade 8 bolts to attach the tow bar on and have a bar between the front mounting points on the Mini as it takes stress off the securing bolts. Use safety chains which are also available at HF.
If using a trailer whether it is a 2 or 4 wheel one get the lightest one you can afford preferably aluminum.

Towbar will put tooo much mileage in your odo and will worn out 4 tires instead of 2 tires (of trailer).  
Decide which is more important to you? Your mini or your Van????

yes.. tow bar   you can buy universal one on ebay. for about $100.. I use them to tow the old split window buses on the RORO boats  going back to england.. they work great.. later  bc

tow bar. Otherwise you're adding the extra weight of the trailer on your tranny.

Do you mean pull it with a tow bar without a trailer when you say flat tow?

sure why not..  might just want to flat tow it.. bc

I tow my mini with my 4cylinder SUV and it work fine.  You should be ok with the 6 cylinder Van. 
I pulled a 700lbs trailer and a 1300lbs mini-- total of 2k lbs, with a tongue weight of 175lbs .  It pulled flawlessly along interstate 5 in california

Does anyone have any experience towing a Mini with a Honda Van? I am thinking about using my van to tow my Mini to an event. Not sure if I will use a trailer or just a tow bar to the front of the Mini. Any suggestions? My Mini has a tow bar attachment already installed.