I'd recommend structures and building systems first because the content of those seemed to have less overlap with other sections. The rest I don't see much reason to do in any specific order - there was quite a lot of similar material between them.

I would suggest to review all of the exams and take the one you feel most comfortable with first. You'll want an easy one first to build your confidence with the testing center location/check in procedures, exam format, NCARB software, etc. 

Taking the 7th test Monday I would recommend taking the difficult ones first for a few reasons.  First if you pass your done and get to finish on something your comfortable with.  Second if you fail you can take the others while the 6 months goes by so you can retest.  Structures isn't as difficult as people make it out to be so don't let that one scare you.  Take a look at the pass rates and base difficulty on these not what you think will be the most difficult.  I found this to be a very accurate assessment of how difficult the tests were. 

I would take CDS first as it requires knowledge of contracts which randomly appear in most of the other tests

After that SPD and PPP have some overlap

I'd take BDCS before Structures, a small amount of overlap.  Many people will say structures is a stand alone exam but if your're like me you haven't though about structures in many years and bdcs will help a bit

BS is a stand alone exam as well - actually I might take this first.  I just took it last friday and have no idea if I passed or not. - very difficult and not something i'm exposed to at work

SD is a fairly easy one to take when you need a break.  I took it first to get used to studying and all that, but wouldn't fault anyone for using another method

There is now a 2 month black out if you have to retake an exam, so taking the most difficult first is less of a concern than it used to be

I second everything shuellimi mentioned above.

Theres 3 years left before ARE 4.0 is retired. If you have CDS PPP and SPD done you will be safe from losing any exams in the transition.

It doesnt really matter which test you take first because you'll have to take all of them in the end.

I wrote a whole blogpost about testing order a few weeks ago. http://www.youngarchitect.com/2014/05/13/architect-registration-exam-take-first/

With the right test grouping you can do it in as little as 5 tests if you haven't taken any yet.

This is what I am currently doing.

Here is the credit model: http://www.ncarb.org/ARE/ARE5/~/media/Files/PDF/Brochure/ARE5_CreditModel.ashx

If you take

Construction Documents & Services

Programming Planning & Practice

Site Planning & Design

transition to the 5.0 exams, you only need to take

Project Planning & Design

Project Development & Documentation

Of course it will have to be done within a certain time in order to complete the 4.0 tests needed before they are phased out and you cannot transition to 5.0.

GRAAD makes a good point which i'm sure will become more popular over time.  

The important thing to remember with that strategy is that ARE5.0 doesn't start until "late 2016." Which means it could be a long wait to save $400.

i think the average person takes a little over 12 months to finish the exams

I can't help it.