"Por cierto" is not always "by the way", and it is wrong to down vote any answer that involves a word/s that are not used in Spain.
The term "false friend word" is only used when two words or phrases in two languages or dialects (or letters in two alphabets) look or sound similar, but differ in meaning.
for sure, by the way, certainly and surely will be correct translations of "Por cierto" depending on the place (geographically differences in the use of) and on the phrase/context.
From sports these days you can see for example on F1 drivers (from non English speaking countries) using "for sure"
Q: Do you have all in place to win the race today?
A: For sure, the team and the car are in optimal conditions today.
A: Por cierto, el equipo y el auto estan en optimas condiciones hoy.
But note that the same could easyly translated to other forms of affirmations like "De seguro", "por supuesto", "Claro / claro que si"
Commonly used in politics speeches the use of "De por cierto, | delo de por cierto"
Q: If you win the elections, will you get us all of this hole ?
A: For sure, I will put this country on the right path.
A: Delo de por cierto, Yo pondre ente pais en el camino correcto.
Expressions and common uses these days
Por cierto, antes de que me olvide => By the way, before I forget
More commonly: (ah, oh) Antes de que me olvide
De por cierto que vamos a ganar => Take for sure that we will win.
More commonly: Seguro que vamos a ganar
Por cierto que voy => For sure I go
More commonly: Claro que voy
Por cierto que parezca no the creo => Fore true that it looks I don't
believe you
Remain the same
Voy por cierto camino => I go true some way/path
Remain the same
Por camino cierto => true the right path
Remain the same
- cierto = true
- por = for
- for true = wrong but the close thing is for sure
You can consider "por cierto" as an expression or phrase that had been replaced by other words and no longer is widely used, despite that, in some places still used in its original form and meaning. It is a word that you can easily avoid and or replace with quite a few others. For sure, if your are not sure about it's true meaning, surely you can avoid it, certainly you will find other words :)