Im guessing you are wondering what kind of tells you are looking for. Well online you dont have much to go with, basically the only 2 tells you are going to be able to pick up on are bet sizing (which is the biggest and best tell you are going to get online) and timing (which will only work in higher buy ins online and more serious games). Those are the only 2 tells youll be able to use online and the thing is, if you are playing freerolls
or low buy ins, these wont matter much because people aren't paying enough attention or caring enough to do anything the correct way.
When it comes to live poker there are plenty of tells that can let you know if a person is bluffing or not. When a person gets very still and doesnt move a lot this is usually a sign that the person is bluffing, if they are more relaxed after they make that tricky river bet they are probably telling the truth.
If they play with their chips and go to make a bet but then pull back and check, this is an obvious sign of weakness and you can probably go ahead and bet and get them off their hand as long as you do it with confidence, because they thought they had a read on you, but they were too scared to actually go with their gut.
If a person checks quickly and then check raises they more than likely have the hand.
There are plenty of live tells to let you know what kind of situation your opponent is in, things like touching of the neck and head and face show stress and weakness.
If someone verbal bets a lot of times its a sign of strength.
All of these are just basic tells, but be aware, when playing with tricky players or more advanced players they may put off false tells, which are signs of weakness that are so obvious that they want you to play back at them, I'll often use these certain things to lure my opponent into thinking im weak when im actually very very strong, it pays me well especially in tournaments. lol Good luck at the tables.