From length: Against notrump 4th best. Against suits 3rd and 5th best (though 7th from a known 7 if seeking a ruff). Always 3rd from even against suits (unless a doubleton or perhaps a 12-pack ;-) ). Again, 6th from a known 6 may be done if requesting a ruff.
From suits headed by AK: Against suits lead the Ace unless unusual circumstances (those that in standard carding would cause the lead of the Ace.) Against notrump lead the King if you want partner to respond with an attitude signal, and the Ace if you want partner to unblock an honor or, failing that, to give a count signal.
From other honor sequences: Top of a solid sequence. From a broken sequence, lead from the more solid part, such that there are 0 or 2 higher cards in the suit. Lead K from KQT4, but T from KJT4.
From 3 bad: Low against suits (though we don't have full agreement there), top against notrump.
To convey attitude during the hand: High discourages a return of the suit, while low encourages.
To convey count during the hand: High shows even, low shows odd.
To convey suit preference during the hand: Standard -- high suggests the higher suit, while low suggests lower.
Attitude, count and suit preference signals: Standard.
Smith Echo vs. Notrump: Defending against notrump, on declarer's
first lead (from either hand), both defenders, unless they are actively
trying to win the trick, signal attitude toward continuation of the suit
that was the opening lead (ignore and give count if it's obviously not relevant).
DTS Home
Notrump Openings
Major Suit Openings
Minor Suit Openings
2-level Openings
Special Doubles
Overcalls and Cues
Over Doubles
Preempts: Ours and Theirs
Slam Bidding
Other Conventional Calls