To hit the perfect nose, you have to
- believe that you’re going to hit it in that particular run;
- land while holding your front wheel down at the perfect angle;
- exit safely without letting your back wheel touching ground.
When you hit the perfect nose and as you exit, you rock your bike in the air (backward and forward at the appropriate time) so that you land farther away with the extra speed boost.
For the wall, @THR_Doucheman’s explanation is on point.