The early stage of a poker tournament can be classed as the first few levels before the antes are introduced.
During this stage of the tournament, your biggest concern is evaluating the composition of your table.
If you know specific players, then great, but if you do not, then you need to go to work identifying potential generic characteristics, such as age, gender, and nationality; commonly known as plain old homework (watch and learn).
When doing your homework, you are interested in the number of hands each player is playing, whether they are limping; raise sizes, three-bet frequency, blind play, positional play, etc.
It is important to gather this information early, and do not just do this when you are involved in a hand. When you are not involved – get involved. Ditch that iPod and start watching how your opponents are behaving.
Once you have an idea how everybody is playing, you can start to develop your strategies and counter strategies.
Which players are the fish, player's you wish to isolate, player's you wish to avoid, etc.
When staring out in poker tournaments, you are probably going to be deep stacked. This allows you the freedom to play more post flop poker, and you can even avoid all forms of three-betting in the first few rounds of a poker tournament.
So, early tournament play is like a recon mission, arming yourself with information, so when the antes kick-in, you are ready to go to war.