Try to section your programs into stand-alone chunks. Turn these chunks into subs; try to test each for all possible inputs and behaviors. Once a sub works, you can use it as part of bigger and bigger sections of your program, each of which should be tested in turn.

As far as standard formatting goes, always write your programs for use strict and use warnings; define all variables at the top of the section that uses them; insert comments wherever you're likely to have problems remembering the mechanics of your code later. Use some sort of standard naming scheme for variables and subs that avoids case sensitivity problems and name collisions.

Read through the posts here every day and try to solve the algorithmic problems on your own. Then compare to posted code. My code formatting got worlds better within a week or two of doing this.