Honestly, I believe it is a matter of a few different variables:1.Your stack compared to the other stacks in your "half", where the bigger stacks are located relative to you on the table, # of tournament entrants. So I will answer both questions based on these variables.
Large # of entrants:
If you are chip leader and 2nd and 3rd stacks are to your right (cut the table in half, both are to the right of you) Loosen up your preflop raising/3-betting range and stay aggressive (but remember to be selective based on situation. Raising and shoving every hand will get you busted). PLAY FOR THE WIN REGARDLESS OF OTHER FACTORS UNLESS YOUR STACK DWINDLES.
If you are chip leader and 2nd and 3rd are to your left, keep your raising range at high value (high suited connecters/1 gappers and premium hands). Stay aggressive. TRY TO MAINTAIN CHIP LEAD TO FINAL 6 PLAYERS AND RE-EVALUATE.
If you are chip leader and 2nd and third are split left and right, use above evaluation factors and play according to which side 2nd place is on.
If you are 2nd or 3rd, evaluate your play same as above based on where the bigger stacks are except tighten up your 3-betting range.
If you are lower/top half (4th or 5th), Keep a tighter range and stay aggressive. Try to move up spots and get it down to 6 people and re-evaluate.
Tight aggressive whole way and re-evaluate based on previous rules every time a player gets knocked out. I'd play to move up payout spots since in large # of entrants tourneys the payouts jump relatively big per place at the FT.
Low # of entrants:
When low number of entrants I always play to win because once you've passed the bubble the price jumps aren't big enough to justify trying to sit out to move up a pay spot. So with Low # of entrants I'd say gamble a lot and stay aggressive.
Now, lets also point out that this may not be relative when getting into tourneys with large buy ins because in a $500 buy in tourney, a single prize jump is much more significant than a $1 buy in tourney in "real life" value. However, if I'm in a WSOP
tourney, I play for the bracelet/ring because the jewelry means more to me than the cash.