How do hot air balloons navigate? Hot air balloons are quite obviously carried along with the wind, so how can they be navigated?  Choosing the correct launch point relative to the desired landing point would seem to play a major part of this, but logic states that it is not always possible to choose the best possible launch and landing points.

Can a hot air balloon be "steered" by increasing or decreasing altitude, hence selecting just which wind it will be subject to?  Does the direction of the wind vary with altitude, and if so, how much?  How do balloon pilots know how the wind will vary at altitude if that is the case?
That is exactly how balloons “steer” - they pick an altitude where the winds aloft are going the way the pilot wants to - assuming winds at an available altitude exist where the wind is what the pilot wants.

Many balloonists use Ryan Carlton’s wind tool found here to get a good idea of local winds: http://ryancarlton.com

NOAA has a website called RUC soundings that presents actual wind and temperature aloft data from balloon launch sites and then interpolates for locations in between: https://rucsoundings.noaa.gov/

While the pilot can plan a flight and do amazingly well to get near to where they wanted to go, at the end of the day, a balloon, as an unpowered aircraft, is at the mercy of the winds.