You will need to change your playing style many times within a tournament. And it is not a constantly increasing spiral of aggression.
I dont think you can narrow it down a great deal (in terms of when exactly to change, and what to), apart from the fact that aggression levels should generally increase in the lead up to the money, and as tables become shorthanded (eg final table).
Each tournament is different. And adaptability is important.
At the beginning you should obviously consider blind speeds, starting chips and payment structure. Is TAG really what you want for this particular tourney?, and if so what form of TAG?
As the play evolves your strategy can and should change alot according to how your stack develops or dimishes, relative stack size, blind level, how your table image is currently at the table, how the others at your table are playing, and how specifically a player you are up against is playing. If a player cant evolve their play continuosly in order to take into account all these factors, then they are doomed in the longterm.