I'm going to give a rundown (and repeat some of what
@hereforthechurros said) just in case....
Poly to MK
1) Resort Monorail (will make a stop at GF before continuing on to the MK station)
2) Resort Launch (small boat that runs in a Poly-MK-GF loop, departs from Poly marina)
3) Walk to the TTC and take a) the MK Ferry (large two-story boat), b) the Resort Monorail, c) the Express Monorail
#1 & #2 are going to be the preferred options for most.
Poly to Epcot
1) Walk to TTC and take the Epcot Monorail
2) Resort Monorail from Poly to TTC (will stop at GF, MK, CR, then TTC), transfer to the Epcot Monorail
#1 is your best bet unless walking a medium distance is a concern. Note, both options require two security screenings... once before boarding the Resort or Epcot monorail and then again at the Epcot front entrance (an unfortunate byproduct of the Epcot monorail station setup).
Poly to AK/HS/DS
1) Bus
Hope that helps!