Same style of leads is used against both suit and NT contracts, in partners suit and during play.
I) Honour Leads (honour = AKQJ10(9))
A asks for reverse attitude (if dummy has a singleton then partners signal becomes suit preference)
K asks for reverse count
Q asks for reverse attitude (if dummy has a singleton then partners signal becomes suit preference)
J promises the 10 (partner usually gives a reverse count signal)
10/9 promises either 0 or 2 higher honour (eg 109x, 9xx, KJ10x, Q109x). (partners signal is reverse attitude)
Lead honour from a honour doubleton
ii) Leads from length with an honour
Usually lead low (4th best) unless obvious reason not to. If leader has “suggested” a 6+ card suit then lead 6th best.
Iii) Leads from length without an honour
Usually lead 2nd highest from four or more (play (original) 4th best next round)
Usually lead top of three small cards (next card is suit preference)
Usually lead low from a small doubleton
Basic principle is reverse (attitude and count). Unless the lead specifies reverse count is the default unless it is clear that attitude is more appropriate. Suit preference is also widely used and particularly in trumps.
Basic principle is reverse (attitude and count). The default is generally attitude but may be count or suit preference in circumstances where it is more appropriate.
Lightner double (usually of a slam) – requests an unusual lead (partner will usually have a void)
Following a double of 3NT (no bidding by our side) – lead dummys suit or if no suit partner has a cashing suit; (dbler has bid) – lead a different suit; (leader only or both have bid) – lead your suit. If partner doubles a cue bid of a suit he has bid it suggests a different lead; if partner doubles then it suggests leading the suit