Since players are always looking for an edge, lots gets written about online tells.  While everybody realizes that betting patterns are the most important thing, everybody is looking for a little extra edge.

1. Timing tells--I know I'm generally a pretty fast player---here are the reasons I might take some extra time.
-am busy at another table
-have to answer the phone
-have the nutz, want to figure out the best way to get all your money
-your big bet pissed me off, I'm going to fold--but I want you to sweat a call
-am checking my e-mail
-near the bubble, want somebody else to bust out
-have read in several places that an immediate bet means a bluff---not for me

2. Typing in the bet size (instead of clicking the box)
I have read that this means a bluff--my observation is that somebody is bored and is playing around

3. Chatting/Insulting--have no idea what this means

So add your observations the list

Can't stress enough how note taking over the years has helped me tremendously.

I believe paying attention to what you are doing and staying focused is a big part also. Always being ready to pounce when the time is right. If you are multi tasking, a bad play may slide your direction but you won't catch it if you are not paying attention.

There are certain characteristics to certain types of players.  If you corner a player's habits into a certain type (LAG, TAG, rock, maniac, etc) you an figure out the tells.

Timing -
Many a time i've seen people wait into extra time and then bet when they have the nuts.  they were slow playing to begin, insta calling all the way, and then all of a sudden on the river they have to think about it and then shove.
I've heard plenty of times that insta calls generally mean that the person is on a draw.  That tends to be the case in most points.

Bet sizes (typing in bets) -
I do it.  I'm not a bluffer (for the most part, still working it into my game).  It's more consistent for 3/4 pot bets, value bets, rather than the oft seen "i have a pair, so i'm going to pot bet it 400 when blinds are still 20/40".  Pot bets don't require any thought, and make the game very 1 dimensional and short sighted.  Varying the sizes of bets into quarter intervals, or even thowing in a dime somewhere, that changes things up a bit and makes players have to think, bluffing or not... and sadly, once this happens, they tend to fold.
Idiots who bet 666, 420, and 777 are mouth breathers and should probably have been left with their heads stuck in their cribs as babies.

Chatting / insulting
Insulting means the person is venting, or just being a douche (hello).  A lot of times in the right cases, it's a sign that the person is tilting...  That's all i got for tells, but this is a valuable tool none the less.
If you are able to multitask, ie. think about hands and have conversations, even typing, then you are ahead of the rest.  If you're able to goad someone into a conversation they don't want, or that is hostile, it will fluster that person.  They will be thinking about the conversation and not the hands they play, they will call something they dont want to call, and basically bleed their chips away.  It seems a juvenile tactic, but if you perfect it you'll be distracting people without them even knowing it.  I've taken a few people out not by taking their chips, but by them not realizing what they're doing (if they knew what they were before) and other people taking them out. 

Disclaimer - usually these people do something or say something that puts a verbal target on their back, like insulting another player, saying "ty" when noone said good hand, basically being a douche.

Ahhh, but how many tables someone plays is another tell. If they're playing at only 1 table, they're weak. If they're playing up to 6, they're a decent player, or they think they are. The more tables they're playing above 6, the more automated their play will be, and ... the easier they will be to 3 bet bluff from the blinds when they open raise on the BTN, for example.

Sometimes I play 1 tournament or 6 but still focus on what I am doing and not others. I mess with my timing so people don't have a clue where I am at. Some people are automated but don't count on everyone to be easy pickings. One table does not make a player weak imo.

Poor choice of words on Fletch's part.  But his point, I believe, is that it's a general indicator.  Like timing tells, this isn't an exact science (Kash in particular doesn't like playing more than 2 tables, and for that matter neither do I).  But it's info that is generally indicative.  Much like playing against hand ranges, you can't be certain you're right, but you can get an idea of how often you are.

Yeah, like Six said (wow, I can't believe people remember lol but I must say it often enough though) I don't like playing more than 1 or 2 tables tops.  For tournament play if I can get away with 1 table (same with sit and goes) that's what I do.  Cash games is a different story as I have been playing 2 tables more lately and may add some still.  Most times though I'm still playing 1 table.

I just find that I can focus more and get better results this way.

Interesting topic for sure.

Just a comment regarding the posting of the big blind as you sit down.  I don't think it means a player is bad at all.  I have posted in the cutoff many times with great success.  Great spot to have a random hand and with limpers in front of me I can see a flop many times with absolute crap and I have won some huge pots because of this with cards I wouldn't have played.  Also I can steal with any two cards from here.  Finally I have position on everyone except the button on flops.  In closing there are advantages to posting before the blinds hit you.  Of course I don't post UTG for example.



Kash

Another idea with multitabler (excessive, not just a few) and a 1 table player...

the 1 table player is and will be more focused on what is going on around them (unless of course they are also watching porn or some Sanford and Son marathon).  This means they are going to try to play their a-game, rather than play the cards.  excessive multitablers will more often than not play their cards and not the players.  I've had one multitabler i've run into a few times (who is a hit n runner too) call me down with nothing but Ace face on a completely whiffed board, and another with KQ off, with raises pre and constant betting, giving me half their stack.  Knowing they play cards and not hands or players gives you an idea that if you have it and they're in the hand, you'll get money... when they ARE in a hand, since they end up being autofold unless they have something.

Every orbit you are paying a blind and a half to be dealt 6 or 9 hands and to be on the BTN and the CO. Paying a blind for half the number of hands and, most importantly, to never be on the BTN is just burning money. You are, be default, going to be readless of all the players at the table. Better to sit out and observe until the BB gets to you ... imo.

Color coding and notes are key in MTT's to me,
 but if i see a player at a cash game I disreguard the notes unless i have cash notes on that player