Code structure matters in a sense that it helps one to organize one's code. Structured code is easier to debug, and easier for "groups" of programmers to contribute to.
There are numberous ways to do so. Elementary examples include stuff like how you organize your loops:
for y = 1 to max
for x = 1 to max
paste image 1, x*64,y*64
next x
next y
gosub move_player
notice that throughout the for loops, their were indentations for each section of the loop. There was an outter loop: y and an inner loop: x. the move_player subcommand really has nothing to do with drawing the map, so I made sure their was at least a line between that and the for loops. This is just an elementary example.
Oh yeah, don't forget to
comment the heck out of it!
"I need gopher-chucks!!"