AK-MK: I like going over to Contemporary and walking it, but you can also do AK to TTC and over by monorail, or Poly or GF and over by monorail
HS-Epcot: What end of the park do you want to be at? Future World or World Showcase? If FW, take the bus from DHS to Epcot. If World Showcase, you can either walk over (it's a long hike) or take the boat. In a hurry? Take the boat to Yacht/Beach and walk the rest of the way.
BB-Epcot: Again, it depends on which end of the park you want to get to. If you want to get to FW, take the bus from BB to Epcot. If WS, take the bus to Beach Club and walk to the International Gateway.
TL-MK: Same as AK-MK.
Buses only run from the hotels to MK and from TTC to MK. Epcot has no bus that runs to TTC; only the monorail. You can also get to any theme park from the TTC if all else fails.