Step 1: Have 3 special Pokemon. The first two are optional, and should be fainted unless you want to switch to the 3rd Pokemon. The 1st Pokemon should have the ability Suction Cups, the second should have the ability Compound Eyes, and the third should have the ability Frisk, and the move Thief. The Frisk Ability is optional.
Step 2: Go to one of the routes with Luvdisc. I recommend Route 8. Then go fishing. Make sure that you use the Old Rod when fishing for Luvdisc, or you have less of a chance of catching one.
Step 3: Use the Pokemon with the move Thief to steal the Heart Scales from the wild Pokemon. Make sure every time you get one you take it from your Pokemon, otherwise they won't be able to keep the next one.
And then do what you want with your Heart Scales! Take them to the Move Reminder, or cash in. But they're only worth 50 PokeDollars, so it's gonna take a while to get a lot of money from this.
Step 2: Go to one of the routes with Luvdisc. I recommend Route 8. Then go fishing. Make sure that you use the Old Rod when fishing for Luvdisc, or you have less of a chance of catching one.
Step 3: Use the Pokemon with the move Thief to steal the Heart Scales from the wild Pokemon. Make sure every time you get one you take it from your Pokemon, otherwise they won't be able to keep the next one.
And then do what you want with your Heart Scales! Take them to the Move Reminder, or cash in. But they're only worth 50 PokeDollars, so it's gonna take a while to get a lot of money from this.