you can't
There is no other way, unless you were to trade.
dig unerground for a fossil
you have to have action replay and then go to game cheats.com and it will tell you
the only way to get deoxys is: a)action replay/r4 b)migrating c)trading
you have to trade/migrate it from a different game that has a deoxys or buy a action replay
You cannot find a deoxys normally(during game play). but you can get it during an event. first you have to get a mystery gift. if you do not have the mystery gift, it is explained on the Pokemon website. there is no deoxys event currently going on.
If You Want A Deoxys In Pokemon Platinum ,Migrate,Trade,Or Use The Action Replay Pokemon Modifier.
action replay
action replay
u will have to get an action replay and find the code online for Deoxys.
i did not catch deoxys without action replay it is really easy with action replay