“Longer First, Higher Rank First” is one of the first commandment in a standard bidding system. This principle governs how you bid your suit.
So, if your hand have a 5-cards suit and a 4-cards suit, it is imperative that you bid the suit that has 5 cards (longer) first. Failing this, then maybe you are using a canape bidding system – which I would guess you probably don’t.
Now, if you got two or three suits of equal length, the principle will always ask you to show the higher rank first. For example:
♠KJ432 ♥QT9654 ♦A ♣A (5-6-1-1, 14 HCP – #1)
With the above hand, you will need to open with 1♥ first before rebidding your spade suit. However, it will be the reverse with the hand below (Bid 1♠ first then rebid ♥):♠KJ432 ♥QT965 ♦A7 ♣A (5-5-2-1, 14 HCP – #2)
Now, how about this hand:♠(void) ♥QT965 ♦A7 ♣ AQT965 (0-5-2-6, 14 HCP – #3)
Common mistake: when you have a 6-cards (or more) minor suit and also a 5-cards (or more) major suit, (Basically, your minor suit is longer than major), some people mistakenly (or have been ill-advised by a clueless friend to bid the major first. WRONG – Always bid LONGER FIRST! So, in hand#3 above bid 1♣ first then bid the ♥ next.
