get a bit more specifc...
-Has the bubble burst yet?
-What are some of the individual and table dynamics?
I understand you're looking for specific answers to a general question, but come on, can you offer advice on such a general question?
However, 2 things I might suggest are 1) Position, and 2) first in vigorish (http://www.pokerstrategy.com/glossar...t-in-vigorish/
Of the 2, position might be more defensive, which I guess means that FIV is more offensive.....
Conventional wisdom might suggest you have a bully pulpit, but at only 20 bb, I wouldn't play that card. Save than when you have more than half the chips in play (purely my opinion). With 20 bb's, even a 3 bb hit by the shortie you forced to shove, will effect the dynamics.
At 20 bb (table leader or not) late in a tourney, you are still looking for another double up. Continue on with the patience that got you that far, until your are bigger than 2x average (like maybe 5x).
Then refine. at least, those 2 example up top of this post to get better suggestions.