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There was a post recently that talked about leading an honor if you have shown support for partners suit (they know you are leading from 3) else lead low.
You've got this jumbled a bit. The usual rules are:
from an honor sequence: lead top card of sequence. This unblocks the suit, and can trap an honor in dummy.
from 3 small: lead high if you have supported the suit. Partner knows you don't have doubleton since you raised, & leading high well tell him the honor position.
If you haven't supported, lead low. This is most common agreement, it avoids partner going wrong by playing you for a doubleton & looking for non-existent ruff, though there are still a few adherents of MUD (middle-up-down), and also a few who play non-std low from doubleton (requires pre-alert in ACBL) who would lead high.
from 3 to an honor or broken honors: lead
low. This is a common novice mistake (some taught incorrectly to always lead highest card in partner's suit); low is correct far more often than leading high. This is important because it's often necessary to keep an honor over declarer's possible honors. Leading high will often just blow a trick outright. For example:
Leading low declarer gets one trick in the suit, leading high gives him two.
There are always exceptional circumstances in bridge where you may want to deviate from the usual rules, including but not limited to:
having the ace vs. a suit contract, if you decide to lead the suit at all, one almost always leads the ace to avoid losing a trick to declarer holding the K & a stiff, or the K & a quick discard.
if you have reason to believe dummy holds the stoppers & declarer shortness in the suit, you might need to lead high to retain the lead.
vs. a suit contract, with a big fit & declarer or dummy likely holding a stiff, one might lead high in case you need to retain the lead to shift to another suit.