Perhaps the simplest rule that can be given is, do not lead trumps
when there is a short side suit in the weak trump hand. You will
obviously gain by trumping losing cards in the weak hand.
As it often requires two rounds to exhaust the short suit in the weak
hand, try not to show your intention too clearly, or the adversaries
will circumvent your scheme of “ruffing” by a trump lead. Remember,
also, that you cannot obtain the “ruff” unless you hold, or can make,
an entry card in your strong hand.
When your combined hands contain fewer than seven trumps, the balance
of strength is with the adversaries, and, in this case, unless your
trumps or side suits are exceptionally strong, avoid the trump lead.
With but six trumps and an established suit against you, it would
be dangerous to lead trumps. One adversary must hold at least four
trumps, and it may be that all the remaining trumps are in one hand.
The trump lead would only help the adversaries to make their suit.
When the commanding trump is against you, endeavour to discard your
losing suit cards from one hand on winning ones in the other before
you give up the lead.