on how to go about this.

Start with the "towel" thread a little ways down.

But in any case:  subtlety  is the key.  Do not say anything to the mama-san about wanting a "special" massage, etc.  They may ask if you have been to a AMP before.  Just say yes.

Say nothing overt to the masseuse.  I like to wait for the flip and then smile and make eye contact.  If they smile back, that is when you can make a discreet inquiry such as "Do you do extras for generous gentlemen?"

You'll either get a nod, or they'll shake your head.  Sometimes a gal will say something like:  "When I know you better."  In that case, you'll need to come back one more time before the fun can begin.

Be sure to bring your wallet into the massage room.

There's a lot more to it, but that should get you started

Suggestions ....

I look for a place that offers table showers.  Always take the table shower.  Don't be bashful.  Be confident and classy.  When she cleans junior, smile and make a subtle positive comment, "nice and clean" is one I use.  As the massage progresses, if she is nearby giving a soothing (not therapeutic) back rub, gently and briefly rub her calf.  I try and make some small talk during the session, complementing her on how good it feels.  You have now set the stage.  On the flip, if her hand is lingering around junior massaging just above him, a gentle push of her elbow with a knowing smile may work.  Don't over do it.  You will know by then if it is a no go.  Finally, I find much more success at KMP's v.s. AMP's.  Maybe it is a local thing.  Good luck!

You arrive.  
Get shown to a massage room.  
You are given a towel or robe, house fee is collected, she steps out with fee while you undress.
You are taken for a table shower (always accept the table shower).
You are taken for a sauna (I pass as heat is not good for me).  
Return to massage room for massage.  At some point during massage, she'll mention that you have not given her anything or sometimes suggest a fee depending on the servises offered.  
You dress & leave
The End.

There are some similarities between AMPs in different regions but there can be many differences in the details. Within NYC, there are different SOPs. Some places are prix fixe (pay one fee for the entire standard menu). Some places collect a house fee (seating charge) and you negotiate additional items with your hostess, typically totaling about the same as the prix fixe places. In some places, there is an option to order from the deluxe (GFE, GFE+) menu at a higher price. In NYC, non-GFE is standard fare for basic service; in LA, GFE is the basic standard. And it varies within the variations.

In some places, there are plain massage rooms with a massage table and towel racks. In some places, the accommodations are more cozy.  

You seem to be in DC. You should read reviews for your area. (I know of only AMP in your area and they are a little more upscale.) If you have additional detailed Qs, you can try the local DC board ... without being too explicit.  

Good luck! Have fun!

In my experience in the southeast, if the lady is modestly dressed, wearing street clothes or a uniform, extras might be difficult to negotiate.  On the other hand, if she's fetchingly attired, like she'll be spending a night out on the town --short tight dress, makeup -- extras will be available for a fee.  Only my experience, though.

Medical Profesionals.  Typically they'll dress in correct medical attire:  these days scrubs are most common.  I LMT told me that she could be disciplined for even having an extra button undone.  They certainly will not be showing cleavage.   One lady allowed touching & undid the front buttons for me.  
This is a good tip.  I'd not expect extras from a legit LMT.  They will keep the drape on & there will be no accidental touching.

I am sure others have said it but here is my experience.

If you know the place is a FS or HJ place. Odds are you wont have to worry about it.  They will make the move.  Just make appointment and show up.   Don't say anything at all.

If not or you are trying a place out.    Here is what I do.   again make appointment and don't say anything about wanting "extra" service.

1. When they tell you to get ready on table.   Strip down naked and not put a towel around you.  Just leave it at the side of the table or on a chair.    

2.  When you get a chance slowly or try not to make it too obvious but touch them... on the leg.  Do it in a gentleman way.  If they move your hand away.... or move away so you are not touching them.   Then it might not be a go.

3.   On the flip, smile at them make eye contact.   If they smile back a few times is a good thing.  

4.  Again initiate contact of some sort.   If they move your hand away or avoid it.  No go.

5.  If she is kind of lingering around your junk.... grab her hand gently and move it towards your unit.   She will either say no, or go to work.

Now for FS places.....  typically the same routine but on the flip... they will know what to do if they don't avoid contact.

good luck

Very good points were made by the others in this thread.

First of all, I need to prove myself as a customer who understands the system. I immediately ask about a table shower. That seems to indicate to them that I'm a knowledgeable customer. However a table shower doesn't fully indicate level of service available, as I've gotten a table shower not only at FS places but also some where the lady remained fully clothed and only offered a HJ.  

If they leave while I disrobe, even if they indicate a towel for my use, I make sure to remain uncovered when they return, and I prefer to be erect for them to see. This again is an indicator of my state of mind and they will often grin and comment on it.  

While in the table shower or the massage, when on my stomach, any attention to my butt or near the twins, I indicate pleasure either by movement or verbally.  

While on my stomach on the massage table, I try to let my arms hang over the side. When the lady is on the side near my arm, I caress her calf. If no protest, I'll caress higher with each succeeding contact as she moves from side to side, going all the way to her tush. It is not unusual to find they have no undies on, in which case I'll caress that area, too. (I'm much bolder than when I first started out! Recently after having caressed the front of her panties, when the lady was standing at the end by my head, I reached up with both hands and pulled her panties off, which made her giggle.)  

If they still have clothes on when they ask me to turn over, I'll ask them to take their dress off. If it is full service they usually will, and I'll get up and sit on the side of the massage table, take them into my arms and begin play.  

Even if the place is FS, if you just go along with them, they'll try to make the massage last long so the playtime is short. But if you do it right you can get that started earlier. If they wanted to work on my back too long, I've rolled over, rose on an elbow and said, "Let's do something else." If they ask what I want to do, I reply "Everything." If "everything" is not on the menu, they'll advise what is.