Power steering fluid was very low on our 1998 A4 1.8T quattro manual.
Filled up the CHF 7.1.
Son reports fluid is low again (say: 2 weeks, less than 500 miles).
I currently don't have the car here, but want to prepare for the fix.

What are the 'typical' parts/locations where leaks occur on the AEB engine?
- pump?
- connections/lines at reservoir, pump, steering rack?
- rack itself?

Whats the best way to locate the source of the leak?

If steering rack (haven't done one yet): any good write up how to fix or change?

 

Check all the hose connections first. Sometimes simple clamp tightening or replacement will do the trick. Also check around the pump. If there are no visible signs of leaks i would check the rack boots for fluid (they will be looking pregnant).
If the rack needs replacement it is a PITA!
BTW , the proper fluid for your power steering system is CHF11s

 

Plenty of possible leak points. Even where the hose is pressed on.

Fluid container with mounting parts, hoses. Fits: Audi | Jim Ellis Audi Parts

 

As an example of what cincyTT said, I had two separate leaks in my power steering system not too long ago. First one was a pinhole leak in one of the hoses itself, which I immediately replaced. That fixed the problem for a few weeks until I noticed a much worse leak. After a very brief search (engine running, having an assistant turnining the wheel lock to lock) I found the seal for the PS pump pulley was spraying fluid all over the place. Since no one sells the seal itself I had to replace the whole pump. Haven't had a problem since though.

 

As noted above, check the inner tie rod boots. If they're leaking fluid, your rack seals are shot and you'll need a rack. It's a pain in the *** due to inconvenience but technically it's a straightforward job. Look in the DIY subforum - I put up a DIY procedure after a rack replacement that i did awhile back. It will walk you through the process. Read through it to get a worst-case scenario of what you might be in for.