Here's my list.

1. Having my balls licked while my cock is in the other girl's mouth.
2. Having one girl bouncing on my cock while the other is sitting on my face. Bonus points if they're dfk'ing.
3. The two girls, side by side AUFD, me alternating between them.
4. Them in 69, me alternating from pussy to mouth (covered, of course).
5. Me watching them do just about anything.

It helps if the girls are truly BI and not just gay for pay.
I also had one double were there was NO girl on girl action  
and that was very disappointing... who am I kidding ... it SUCKED
It's not a bucket list thing if you have a really good double.
It's just something that you want to repeat :

You hit the nail on the head; two ladies who are truly into each other. I like to just watch them do each other as much as I enjoy having both of them do me at the same time, or any combination thereof.

I need a good doubles experience every few months. Come to San Diego sometime and help me out!

My current favorite has a friend whom I've also seen. So I thought it would be fun for all three of us to get together. At the end of two hours, we were all completely exhausted but grinning from ear to ear.  

Still remember that time vividly. What an experience.

I would like for them to make out with each other with my cock in between their mouths.

Damn, now I'm going to have to go rub one out, lol.

To me, getting a chance to bang two chicks at once ... was a personal milestone.

It meant that I had arrived in life. After all of my years of hard work, eating shit, suffering through crappy jobs, relationships that never seemed to work out ... I finally feel like I have my shit together and my career is headed in the right direction. And I now am in a position where my entertainment budget will allow for such luxuries as ... banging two chicks at once.

So to the victors go the spoils.

Duos are mans best friend!  

Rarely does it happen in the Civie world so my first time with professionals
opened a new world that I now enjoy at least a few times a year.

The key is knowing at least one of the providers well and
her knowing her partner even better! IMO

I want the gals to be into each other and trying....

just as hard with one another as with me. Equal play time, equal orgasms.

Too often, it just seems like one guy screwing two gals one after the other.

...oh wha the hell....throw another one on top of the pile

i guess it's on my bucklist too.

I once had a duo session who was interested in doing duos with me but she really wasn't into it. I think she was only in it for the exposure and money. When I kissed her she was stiff and she didn't really play with my sweet spots much. It felt awkward and forced and both me and the client didn't have the greatest of times. Ever since then, whenever a girl wants to do duos with me I tell her to kiss me long before a client ever shows up so I know it's for real and not just for marketing.  

With that being said I really desire a double girl session that feels natural, unforced and very sensual.

I've had a few 3-somes, so it's not just a bucket list thing for me.  I've always done a 3-some with an ATF who was bi- and I let her make suggestions for the 2nd provider.  For a good 3-some, the 2 ladies really need to be bi- and into each other, otherwise things aren't as "interactive" and fun for everyone involved.

Anyways, most of the time we would just go with the flow and let things progress naturally. Occasionally, my ATF would direct the action between her friend and myself or vice versa which sorta made it feel like we were making a porn movie. LOL!  One thing I would recommend is to use female condoms, so there are no breaks in the action when moving from one lady to the other.

In the last year I've enjoyed 9 3somes. I really enjoy the constant immersion of stimulation that two gorgeous women can provide. Different techniques and different acts. The added visual of them pleasuring each other and reaching for me to join in is so much fun. Two hours of non stop pleasuring.

Now to set up another! Perhaps I might add a third lady.

I have been in threesome in some different circumstance. . I used to have a bi sub GF who had a number of female friends who liked to join in.  One or two like us both to dom and sexually use my then girl friend, there was one who liked my GF to co dom me with her.  
Most often tho it was a threesome with two women during which we all were into each other and having fun and being into it.  
One experience I had trouble with was with a friend with benefits who is very very sub and whose husband was even more so and bi.  She finally got me to join them where my role was to dom them both and --among other things-- use the husband sexually while he was restrained and "forced" to submit while his wife kissed and caressed me and humiliated and spanked him.  I really could not get into it.  My sub  female friend said she was surprised at how suppressed I was.  I was a little surprised my self.  
In the end, I love the experience when the three of us are all enjoying each other.

My main desire is to be with a lady such as Brenda Boobies who is truly bi.  
I've been in a few doubles where the lady is play acting and that's just a turn off for me.  
I agree with Brenda about making your fantasies come true if this is one of them.
From the opinion of one of the girls is that I want both to be into it and have a fun time.
Not just be there because you have to be there.  
There's nothing like having a girl text you and say I'm so excited about being with you today and truly mean it.
I'm sure you fellas know what I'm talking about.
I've also seen couples where the woman has wanted the date as much as the man, if not more. That's a turn on to me.
As truly bi-sexual woman I enjoy having a man and a woman in bed with me.
I definitely think the chemistry has to be right, and yes Brenda Boobies and I have great chemistry.
I cannot wait to do another date with her soon!

I indulged quite a bit with two gals.

My shtick was to find two bi gals to get it on with each other while I watched, then have them profess to need my manly appendages to take their joys to fruition.

It was a blast when all went well.

But after some time, the thrill tended to wear off, and I found myself physically taxed at hosting two gals simultaneously.  I switched to the tag team approach, but even that seemed to lose its allure as  well as bang for the buck argument.

Now I'm pretty much a one gal (at a time) guy

But I have no desire for a threesome. I'm way too afraid that they would be more interested in each other and ignore me. I don't need to pay for rejection.

Hmmm... Great question.  I've had a double date yet but am always open to one.  One provider I saw last spring suggested a double date but things never came to fruition.

I think I"d want the girls to definitely be into  eachother.  Talking dirty and teasing me  during their time with one another.
A two on one BJ would be nice too, with the end result being shared.
One on CG while I ate out her friend and then switching.
If I last this long (lol) have them both get in doggy position and I take turns pumping  both.

D

Well, as for me, being the date in this absolutely exquisite courtesan sandwich was perfect, there is no better way to describe it. It is definitely a bucket list kind of thing, but the ladies need to be into it and each other too. I've been in one other that was completely mechanical, but with Jade & Brenda it was just fantastic, participating as well as using the mirrors over the bed (thanks Jade!) to watch these two stunning women enjoy each other made the date one of the best of my life. The chemistry was perfect, the ladies were perfect, it was magical