Runners move around like regular baseball. I always try to design my dart games as close to the real game as possible.  Each time you get a base hit, all runners move the same number of bases.  Say you get a single then a double, you would have runners on 2nd and 3rd.  If you get a double then another double you would drive in the guy on 2nd base and score a run.  The balls and strikes work just like a normal batter 4 balls you get walked and get a new runner on first.  3 strikes without throwing an out or a hit you would get an out.  One player throws until they get 3 outs then its the other players turn.  9 innings to see who is the winner.  I am working on scoreboards too which will be chalk board and chalk.  There will be an outline of a baseball field then you could chalk where your runners are.  There will also be a spots to mark balls, strikes, runs, etc.  The scoreboards will come as a separate piece or I'm designing a cabinet that will hinge around and cover the board and when you open it there will be a spot to hold darts on the left inside and a scoreboard on the right inside.  The great thing about my games is that you can always think up your own rules and play however you want!  Just have fun!