One of the most important factors to bear in mind when getting involved in a poker tournament is that a tournament, unlike standard one-off games, offers different rules for profitability than you as a player may be used to. Unlike normal poker games where each hand can mean more or less money, in a poker tournament, only the top positions are paid out and realize some sort of return, meaning you are aiming to be the best of the best rather than simply a good player joining in a friendly game.
To achieve that high position, your first goal should be to establish yourself with a strong chip base early on in the tournament in order to better prepare for later rounds that will be the key decision makers as to whether or not you will come out in the "bubble," or the paying bracket of the tournament. In order to reach this goal, your early tournament game needs to be just as solid as your late game moves, while risky wagers should be avoided at all costs. It may seem like a good idea to jump in and try to snag a huge pot early on, but unless you have particularly strong cards and feel confident you can beat your peers in this regard, this sort of move should be avoided at all cost, as it will more than likely result in you lessening your position and compromising your ability to come out ahead in mid to late-game plays. Instead, focus on playing tight with an occasional bluff of blind steal that may only give you small chip gains but will help ensure a regular increase rather than decrease in your stack.
As the game moves towards later rounds, now is the time you need to play more aggressively, targeting mid-level chip stacks in particular, if possible, or taking out players with larger stacks that may have grown over-confident in their abilities after earlier rounds. Your goal is to give yourself a strong enough stack so that as the blinds increase, you need not worry about being caught short and potentially knocked out after all of your hard work. Still, do not over-extend yourself - play your cards tight, if possible, in order to prevent any lower-level players from coming in and knocking you out of your position. However, at the same time do not play too tight as to not allow yourself the much-needed chips for later rounds.
When the final rounds come up and only a few players are remaining if you are not already in the bubble, then work as consistently as you can towards placing yourself in a position to get there. This may mean taking some larger risks than you may have been willing to take earlier, but by now, you should be at a stronger position because of your earlier financial gains as well as your observations of other players. Your goal is to try to catch other players in small moves that can bring you a big pot, particularly if it may be a game-deciding hand.