Is there a way that you can ensure being difficult to predict at Poker? For example, if you never bluff, people will eventually get to known that and it will reduce your ability to profit from good cards? Anyone there knows techniques or trick to avoid being easy to read?
What you ask is known as balancing, but it is only worthwhile to start balancing at medium levels. At micro limits or at the lower levels of land based casinos, people don't think too much. At those levels it is enough to select your starting hands well and bet for value aggressively.
When you go up levels, you will find more opponents who think and pay attention to what you do. So, if you are one of those who only bet when you have good hands, they will not pay you for value, and if they do it will be because they have a better hand than yours. This is where the concept of range balancing comes in. For preflop plays, for example, let's say a 3bet range of value is TT+, AJs+; Aqo+. If you want to balance you have to put into the range other hands that are not as good but may have good postflop playability depending on what comes out, such as 22-55 or 78s-TJs.
For postflop play the same, you can't just bet or re-raise only when you have a good hand, you have to start doing it with other hands, and it's better to start with semi-bluffs and later on you will put in pure bluffs.