put 2 pokemon that u want on a high level in the daycare next 2 mauvile city,then go 2 the
desert sandstorm on route 111  go up and u should see a little ''mud slide'',then find
something 2 hold down the up button on ur directional pad(plug in ur charger 1st!) and
leave ur GBA on all night and ur character will be trying desprately 2 get up the "mud
slide" but will fall down every time. so each time u take a step up(and down) the "mud
slide" ur pokemon will gain 1experiance and when u go back ur pokemon will be ungodly
strong!   P.S. try it it worked 4 me