After the first post for beginners, I can write much more original about this topic.
First of all, I would like to point out that I play almost exclusively in the $1-10 buyin range, so my personal experiences are from there as well, and about freerolls, and some comments will be specifically about freerolls.
1., Wherever you look on the subject, the general opinion about limping comes up everywhere. (Limp: most of the time it means the call of the big blind.) For me, there is no question that this is the most easily detectable characteristic of losing players. 100% in the long run you can only lose with it, yet many people play this way in freerolls. As long as it is used by only 1-3 players/table, it is possible to gain an advantage even in freerolls. Unfortunately, if more people play this way, it becomes much more difficult.
For this reason, anyone who wants to move on from freerolls should definitely count on this. This is a typical freeroll 'strategy' as there is no buyin cost. I personally do not recommend it to anyone as it is against the most important law of poker. Namely: you only have to win the blinds in every round and you are a winning player! Later, it is also difficult to switch to real poker, where there is almost no limp at all. The only exception to this in the short-stack game is the SB vs BB call (limp).
2., Always check tourney structure! Most tournaments start with 100 BB+ starting chips. So at the beginning there is an opportunity to play a little wider. You can raise and call with plenty cards that you have to fold under 40 BB stack. Low suited connectors, which can primarily be considered, but it really depends on the players how tight they stay during this period.
3., SB, BB gameplay. Always try to avoid to be the hero from SB position. Never really pays off. The BB position should be the one, where from you play the most. Especially in early phase, as you already have 1 BB in the pot, it gives higher odds to get involved in pots, even with cards, what you should ford from early or mid positions.
4., Aggressivity, stealing blinds. That's a must, especially, when you run deep in a tourney. Under 40 BB stack, it is really neccessary, sometimes even with all-in steals from button, SB position.
5., Always take attention to opponents stack size, too. I could write a lot about this, as it changes wildly by the time in a tourney, also depends on the stack sizes (yours and opponents, too) and positions. (There are obvious cases, like you don't get involved in a pot vs. a 3-5x bigger stack size player, only with very good cards, even just the very few premium hands near to the money.)
This is something what players should check out deeper, and keep attention on it, when watch back their games.
6., Bubbles. There are 2 main one: ITM (in the money) and FT (final table) bubbles. Both are important, the first obviously about reaching the money, what usually means you doubled your buyin, so you won. The FT bubble is important, because of the amount you will win. Maybe it doesn't sound like a big difference, you finished in 10th position or 6th, but regarding the money, it makes a huge difference. Usually, the gameplay includes plenty blind stealings, often allin ones in this phase, and the biggest 1-2 stacks can do it with a pretty wild range of hands. (If a player has 4 times higher stack vs. his opponent, he can do it pretty much with any 2 cards pre-flop.)
7., When you get involved in a plot, always plan ahead. What will you do on flop, turn, river if opponent does A, B, C moves. Also play with the bet sizing, how fast and big you want to build the pot. It's also an important topic, as it highly effects how much chips you can win/lose from a given hand.
8., Try to be unrecognizable in addition to not playing too aggressively. For example: different bet sizing with same cards.
9., Patiance. I have to mention it, as in my opinion, that's the most important thing what you need for poker, especially for online poker. Yes, you will have incredibly bad runs, but if you are confident about what you do, you know your odds, generally the math part + the what moves are profitable in given situations, you won't end up with loss in the long run. When I say long run, I mean it. Not 10 or 100 tourneys, not even 1000, much more, especially if you play big field tourneys over 1000 registered players.
10., Earlier or later you will reach the heads-up situation, when only 2 players left in the game. It doesn't happen often, and the pay jump is the biggest between 1st and 2nd position. I am personally not good in that, even I practice it time by time in Heads-up sit and go games on the $1-2 limit, but still I have less than 50% winning rate from tournament heads-ups. So probably I am not the right person to say anything about that, but again, it's something very important.
Suddenly, that's what came up in my mind. It wasn't a visual topic, maybe next time.
Good luck at the tables!
100% beneficiary of this post is @the-dealer.