So far I've been picking them when

Fig changes color
Fig stem changes color
Fig droops down
Fig get soft
Sometimes has sweet liquid leaking out of the skin or eye
Cracked

Is there a definitive way to be sure I'm picking them at their peak ripeness?

That sounds right.  Drooping and becoming soft are great indicators as well as skin cracking.  Wrinkling is a good indicator for different varieties.

sirlampsalot informed me that once it's picked, if it exudes that milky, latex sap, it's not ripe! So, you want to make sure you don't see any of that when you are picking figs.

Usually you see the neck go soft and it droops down, as Herman pointed out on another post earlier, during this cold weather even with the droop this time of year you will most likley need to wait a few more days for it to be ripen, I cannot comment on different locations or varieties but just more as a rule of thumb.

Rich,
Everything that you have listed and a bit of trial and error.
Each cultivar will be a little different, but when the pulp is translucent or jammy, no white filaments, its usually fully ripe. Personally I prefer them when picked at the "almost ripe" stage, as in the 2nd picture...
The pictured figs are #1...not ripe, #2... almost ripe, and #3...ripe.
  

See Harvest.

According to many on the forum, a fig is ripe and ready to pick exactly 1 day after the birds eat it off the tree.
(...you got lots of serious answers, so I thought I'd mix it up a little ;-)
Jim

Rich, you have 6 possible good answers. I like to add one more is using your sixth sense for picking the peak ripeness in figs. All of us have sixth sense, but we do not know how to use it. By using your sixth sense, you do not need to touch a fig, but by looking at it and your sixth sense will be able to let you know if is ready or not. Thanks.

Best,
Tam

I'm a premature picker. It's all I can do to not pick one that is soft right now, but I don't think it's done cooking yet.

i usually pick one for test. i wait till most of the fig is soft and looks like it won't bleed on me. then i pick on to see how ripen it is. once i do that, i know how long i'll have to wait for the rest. but lot also depends on the weather, birds.. tree rats.. other rats.. i'm keep finding that there is something big enough to take a bite out of figs on my tree this season. not sure what that is. can't be human since the part of the fig is still attached to the tree.. weird. for whatever reason, the birds are not able to pick ripe figs like last yr. i guess they are just as frustrated as i am and just pecking at the figs.

One of the indicators that lets me know when a fig is dead ripe(especially on figs with lighter color skin) is to wait until the brown spots(sugar spots) start showing on the skin...I have picked figs with all of the above mentioned indicators, and they are definately good, but when I wait a day or two longer(just until the start of the brown spots) I notice a definite increase in the sweetness level of the fig...the only down side is that if I wait too long, then the fig flavor takes a turn for the worse(slightly sour)...so a little bit of experience here pays a big dividend in flavor...unfortunately on the dark varieties it is more difficult to detect these sugar spots, as they blend into the dark color skin. 

Picked a couple nice figs tonight both with sugar spots. Both were very good. My wife even said she prefers them less ripe and a little more firm.