One word:
Chaining
The higher the level on the DexNav on the Pokèmon, the better chance of finding your shiny. It's simple:
Go into the grass and the Pokèmon that you have already caught are registered. For this example, I will be in Route 101 in OR, trying to find a Zigzagoon.
Click on the Pokèmon sprite on the DexNav, there you will see several things:
- The Search Level (mine is 47)
- Pokèdex button, to view the Pokèdex's entry
- The Name (Zigzagoon)
- The Type (Normal)
- The Search button
WHEN YOU FIND IT, THE MORE OPTIONS ARE:
- The Stars (Perfect IVs)
- Held Item
- Moves (They can't usually learn some moves not native to them)
Click the Search button continously until you see arrows that point like > <, >> <<, or >>> <<<. This indicates how far you are from the Pokèmon. Creep on it until you reach it's shadow.
However, this is quite a long process, but it's a better way of finding shinies, unlike the Pokèradar thing in XY.
When you see a ! that means that you have found something special in the Pokèmon. It could be:
- 3 stars (3 perfect IVs)
- An unusual item held by it
- Unusual moves that the Pokèmon can't learn
- A Pokèmon not native to Hoenn or the area
TIPS:
- Never run away from a Pokèmon's shadow. You might not know if it's a shiny or not.
- Try and try again! It might take a while, but the prize is rewarding.
- Collect several Pokèmon. I don't know why this is helpful, because most Pokèmon are way under leveled than yours, but it's better to be careful than to be sorry!
- Always catch Dittos on it's Mirage Island.
With these steps and tips, you will be able to find some shinies!
Have fun shiny hunting!
