What is the best way to lift the tail of the brow: filler, Botox or threads?

That
depends on a lot of things including the age of the patient, the degree of lift
required, the laxity or otherwise of the skin. In order to give you the best
advice an examination in person is essential. This will allow your practitioner to determine the anatomy and the condition of the tissues, and thus what
is likely to work for you.
Botox alone can be very useful, particularly in younger patients,
to give a subtle lift to the tail of the brow. This is relatively economical
but  does require maintenance every three to four months. To enhance the
effects of Botox, it may be possible to add filler directly to the brow or to
the temple thus supporting the tissue around the eye. Fillers may last from 6
months to over a year.
Threads
can be useful for the brow area, particularly where a more substantial lift is
desired, but it must be remembered that the procedure is more invasive, carries
greater risk, and it is more expensive. The effects of a thread lift in the
brow will be maintained for up to a year, at which point you would need a
repeat procedure.
A
combination of all three, fillers, Botox and threads would give the
maximum lift, but will obviously be the most costly option
Please
remember to choose your practitioner carefully. You are looking for someone who
is medically qualified, highly experienced, and who has performed high numbers
of whichever treatment you are seeking.

All of the above can lift the brow.  The choice depends on a number of factors including cost, longevity and severity of brow drop.  Botox is a simple, low cost way to start.  If not sufficient, fillers can help support the brow and provide projection.  Threads will pull up more than the other two methods, but is a bit more invasive and has more recovery.

It depends on how much lift you need.  I would recommend beginning with Botox to relax the muscle, to lift the brow 1 - 2 mm.
If you want additional lift, you could add a dermal filler, as well.
Best of luck to you!

Hello
Botox/other similar agents can lift the outer eyebrow and give a good effect. There are other agents which can also do the same but it may be worth discussing with your local provider first so they can assess you individually and seeing what options they have available. 

I prefer to use neuromodulators like Botox or Dysport and in certain cases, fillers, to lift the tail of the eyebrows. Of course, it is hard to say if either of these treatments is right for you without seeing a photo or evaluating you in person.

That is one loaded question. LOL. The answer would depend on your age and many other anatomical variables. In young individuals the eyebrows are generally lower yet their Fuller in the tail of the eyebrow and if someone wants to make their eyebrows look younger they can have that eyebrow filled out either with a filler or a little bit of your own fat. Botox will lift the eyebrow tail quite easily as long as the muscles are strong enough and you still would need to be evaluated by a plastic surgeon like myself. Threads on the other hand, which I was working on developing in the early and late 90s have not proven themselves to be a long-lasting solution since the first rigorous massage of the face you get, will displace the cogs of the threads and if your face will go back down to its pretreatment condition. Good luck from New York City