How to determine what 即 means in a sentence
Dictionary gives 6 meanings:


  
  就是：知识～力量。
  当时或当地：～日。～刻。～席。～景。在～。～兴（xìng ）。
  就，便：黎明～起。
  假如，倘若：～使。～便（biàn ）。～或。～令。
  靠近：不～不离。
  到，开始从事：～位。
  


With translations and comments, comments in italics:


  
  is:
  
  
  知识即力量 = Knowledge is power.
  This usage of 即 is more formal and less often heard colloquially.
  
  this (time or place):
  
  
  即日 = today;
  即刻 = right now;
  即席 = with improvisation (lit. [in] this seat);
  即景 = the immediate (poetic) environment;
  在即 = soon;
  即兴 = with improvisation (lit. [by] that [time's] mood)
  
  then:
  
  
  黎明即起 = [as soon as] dawn [comes], then [you should] get up
  the example cited is actually Classical Chinese, so you would not hear this colloquially
  
  if:
  
  
  即使 = even if
  即便 = even if
  即或 = even if
  即令 = even if
  I don't even know the last two.
  
  come near:
  
  
  不即不离 = keep at a respectful distance (lit. neither approach nor leave)
  The example cited is a Buddhist term, and I have never heard of it.
  
  to start working at some position:
  
  
  即位 = to start working at some position
  即位 is idiomatic, I would say.
  
  


Finally, a list of the words that you would hear colloquially:


即日 = today;
即刻 = right now;
即席 = with improvisation (lit. [in] this seat);
即景 = the immediate (poetic) environment;
在即 = soon;
即兴 = with improvisation (lit. [by] that [time's] mood)
即使 = even if
即便 = even if
即位 = to start working at some position


(From meanings 2,4,6)