Drill hole through thick wall for TV cable
Not knowing your wall configuration (or even your country), I am going to assume the most common walls for interior walls in the USA.  That is a hollow wall with 2x4 studs with drywall on each side.  You pretty much have 2 choices of how to do this.  One is buy a longer drill bit and the other is do your best from both sides.  A while back I purchased a 1/4" dia x 12" long. It can probably be purchased at any hardware or big box store.   

If you don't want to spend a few bucks on a longer drill bit then do the following:


In the area you want to put the cable through, determine the stud locations.  Either use a stud finder or tap gently on the wall with a hammer and listen for hollow vs more solid sounds.  You will want to avoid the studs for the obvious reason and because there could be wires running along them.
Drill a hole in one side of the wall, using the size of drill bit that the cable will fit through.
Measure where that hole is to a corner that might be common distance on both sides. For example if both rooms are on a single outside wall, measure to the corner on that wall.
In the adjacent room, measure back from the appropriate corner that distance, and the same distance up from the floor.
Drill a smaller hole from this second room.
Have a friend hold a flashlight up against the small hole while you look through the larger hole.  This will let you know if you are close enough and in which direction to try to fish a wire through.  If the hole does not line up very well, repeat the drilling of the smaller hole and checking the alignment.
Once you have good alignment, enlarge the smaller hole.
Tape an end of the cable to a stiff wire (old wire coat hangers were good for this, but now hard to find) or rod (long pencil, dowel), or even a stiff broom fiber.  Basically anything that is stiff and small enough to go through both oles that a wire could be taped to.
Poke the stiff through the hole until you feel it pass all the way through. Once it is through, it is easy to gently pull the wire through.  It might take a second person to help the taped connection get through.
If necessary, go back and repair any of the smaller holes that might need patching.
If you want it to look better, you could use a short cable and purchase electrical plates for cables.  This becomes a connection in each of the two rooms that a cable is attached to.


Personally, it is a lot easier to buy the longer drill bit, then widen the hole a little bit larger. Then  tape the cable end to the drill bit to use it to pass through the wall.  They are not all that expensive and has been useful in many situations.