Here is what I did:

BEC -> AUD -> REG -> FAR

Here is what I would have done if I had known better:

REG -> FAR -> AUD -> BEC

For me, the reasons are:

I was most unfamiliar with tax.  It required quite a bit of work for me.  FAR has the most material, then it is just down hill from there.

Alot depends on how you want the timing to work out.  For instance, if you are planning to take 2 tests in each window, I would not do FAR and REG in the same window, unless you luck into getting one exam on the first day of the window, and one on the last day.  Having 2 months in between is pretty doable.

Basically, this is a long post of saying, it is all very dependent on your schedule, prior knowledge, etc...

MrAudit wrote: Hey, I just completed the application process of sitting for the CPA. Any of you vets recommend which section to take first? The hardest or easiest one first? My main concern is taking the exam in the best order so that none of the section I pass expires in 18 months.... thanks!

I recommend BEC to anyone who is sitting for the CPA exam for the first time.  It's so important to understand the material taught in this section because this foundation will make your life easier in other sections. 

The two doozies of this exam are FAR and REG.  FAR is challenging because of the quantity of material and REG because you have to be quick at taking tests and really know that material so you can get through the material.  You only have 3 hours for REG and this makes the exam challenging! 

AUD it's about common sense and logic!  If this comes easy to you, you won't have a problem getting through it. 

1st BEC

2nd either FAR or REG

4th AUD