What to listen for when setting VTF?


I've read that folks fine tune VTF by ear, so was curious what you listen for. How does more or less VTF affect sound? Thanks.
gbb
If the arm is to high in the back, the treble will be bright and could have "sibilance" if to high. Also, bass will be very thin and lightweight.

If the arm is to low, the treble will be recessed and light in detail. Bass will be "boomy" and bloated.

I agree with the starting point a little lower than level.
The responses above reflect VTA (angle) changes but Gbb is asking about VTF (force) changes.
Sorry, as usual I can't read and/or comprehend. Below is a great link with info:

http://www.soundfountain.com/amb/ttadjust.html#DOWN
VTF and VTA are interrelated variables. As you change one, it affects the other. Once dialed in, minor changes in VTA won't require readjusting VTF (thank goodness for those of us who change VTA for every LP). But changes in VTF always require a re-listen for correct VTA.

To the OP's specific question on VTF, I highly recommend reading the "what to listen for" process posted by Lloyd Walker on his web site: Fine Tuning Your Turntable. I've been using this process for years with great results.
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I don't understand how people can change VTA for different Lps. Wouldn't that change overhang?