A lot of the time the Saying "ONE TWO
THAT WILL DO" is applicable BUT if you open 1♠
with 18/19 points and partner replies 2♠it certainly won't do now DO,
just rebid 4♠ straight away.
If dummy has a shortage and 3 trumps this usually is a sign not to draw
trumps straight away as you will need have any trumps left in that hand,
the short hand to do the necessary ruffing will you?
If your partner balances
in 4th seat and the opposition now bid onto the 3 level DO NOT BID NOW.
Partner's bid has forced the opposition to the three level and now hopefully
they might go one down, now that they might be out of their comfort zone.