I play 3rd and 5th against suits and 4th best against NT.

 

 

So how do you lead 3rd and 5th? Very easy. When you are leading a small card in a suit of odd length, lead the smallest, otherwise lead 3rd best.

I stay with 4th best against NT, because you usually don't lead from 3 against NT. If partner gains the lead, partner must determine whether the suit has enough meat. Knowing that you have exactly 3 cards higher makes that decision easier. Whether you have 4 or 5 is usually not as important.

 

But against a suit contract, your length in the suit that you lead is more critical.

 

3rd and 5th solves several problems.

1. Partner is usually given an immediate count of opening leader's suit length. If the card is the smallest, then opening leader has an odd number. Otherwise an even number.

2. When playing 4th best, leading from 3 was a problem. So playing 4th best usually turned into 3rd or 4th best, which is hard to decipher from only one card. Might as well play 3/5 always and solve the problem. (MUD is ridiculous, so I don't want to talk about it)