This is all about interpreting the strength of the original raise.
Weak Raise = More 3 Bets.
Strong Raise = Less 3 Bets.
Some general indicators:
- An early position raise is stronger than a late position raise.
- A tighter players raise is stronger than a looser players raise.
The exact range you 3 Bet is very fluid but can consist of:
Pairs, Suited Connectors, Strong Broadways.
Reads are very useful regarding:
- Whether the original raise is strong or weak.
- What range the original raiser will call with OOP. What range he will 4 Bet.
- How he plays in a 3 Bet pot.
This post is sort of a summary of other articles here so a lot of this is just me passing on information I've seen elsewhere. Hope it gives you an idea.