Yes you can. It's called chaining.
"First off, I'll assume that you know what both shinies and the Pokeradar are. If not, I'd suggest not reading this, as it'll only confuse you.
Second, I'd like to begin by letting you know a few things you'll need to begin this method. Be sure to have the following:
1. The Pokeradar.
2. Pokeballs (to catch the shiny with, of course)
3. LOTS of max/super repels. You'll need to buy a lot of these, hundreds in some cases. I'd suggest fighting the Socialite and Gentleman on Rt. 212 with the Vs. Seeker and an amulet coin until you have enough for some good repels. You're gonna need them!
4. A strong, high-level Pokemon with enough PP in high power moves to take out a bunch of Pokemon in one blow. You'll want to specialize this in some cases, depending on which Pokemon you'll be chaining.
5. A Pokemon that can whittle your shiny's health down for catching. Obviously, this is optional, but very helpful if you're not swimming in master balls.
6. PP Restoring items. (I prefer leppa berries, as they're easy to find).
Now that we know what we'll need, let's get started! The first thing you'll want to do is go to Sandgem town and find out from Dawn's/Lucas's sister what Pokemon are swarming that day (if you want to chain a swarming pokemon).
Once you know where the swarm is, go to that route, and find an ideal place to begin chaining. (If you don't want to chain a swarmer, go to where the pokemon you DO want to chain is located :p) An ideal spot is one where the grass nearly covers the screen. Once you're there, save the game.
Now, I'm going to introduce you to a method known as "chaining." Chaining is a process by which you "chain" multiples of the same species of Pokemon one after another by using the Pokeradar. When done correctly, you can get dozens of these things in a row, and an added bonus to doing so is that it boosts your chances at finding a shiny Pokemon dramatically.
So first, use a max repel, and then use your radar. Notice all the wiggling patches of grass? I tend to go for the ones that aren't sparkling, as they're harder to confuse with others.
Now it's time to let you know about the "Rules of Chaining."
Only choose a patch of grass if there are FOUR patches shaking. The reason for this is that if you don't see a fourth one, it might be hiding somewhere else, and it could be the one you were supposed to go to instead.
After the first patch you choose, all subsequent patches MUST shake in the same way. Choose any others, and you'll break your chain.
Never choose a patch of grass that forces you out of the radar's range.
(The range is dictated by whether or not you can see at least one of the patches of grass that wiggled.)
ONLY choose a patch of grass that's farthest from you, and is at least four patches away.
Never choose a patch of grass that's more than seven steps away. That's the steps you have to walk, by the way, by taking the shortest route. This is not a calculated distance; it's one you can count by actually walking it. (Someone in here warned us about this, but I can't track him down. If anyone can tell me who, I'd appreciate it; I need to credit him. Anyway, it's turned out to be true for me every time I tried it. If anyone can get it to not happen this way, I'll need to know that too. :p)
NEVER choose a patch of grass that occurs on corners or edges. The fewer empty grass spots that surround your chosen patch, the greater its chance of breaking the chain.
Avoid patches of grass if they are right beside other moving patches. See rule 5 for the same reason. ;)
When in doubt, reset the radar and try again.
If you see a patch of grass that sparkles twice dramatically, and seems to have a differently colored hue, it's a shiny Pokemon. Proceed there with caution! What the grass will look like (video courtesy of Pokerealm)
Never run away from the Pokemon, and never let it flee either.
Never use your bike.
It's a lot to remember, but in time, it'll become second nature. Now, I should address one more thing before moving onto the tips and tricks. Resetting the radar.
Here's how you do it. The Pokeradar needs to recharge after every fifty steps. If you come across a set of wiggling grass that doesn't go by the rules, walk fifty steps in non-wiggling grass (taking care to stay in the radar's range), and use the radar again. This will not break your chain, so long as you are in range when you use the radar again. And believe me when I say this: you'll be doing a lot more resetting than running into Pokemon.
So now you have the basics. Is there anything else you should consider? Of course! Here are a few tips and tricks you might want to keep in mind before you begin:
Swarming Pokemon make easy chains. Swarming Pokemon, and also any other pokemon that are common in an area seem to be easier to keep the chain going. This may or may not be true, but It seems so in my experience.
Never enter the grass directly behind your character. Unfortunately, this grass is mostly hidden from view, and if it wiggles, you'll be hard pressed to see it. I make it a point never to enter this grass unless I can see all four of the wiggling grasses elsewhere.
It's good to have a Pokemon that knows super fang or false swipe in your team. They'll help make the Pokemon easier to catch. Any immobilizing statuses like sleep or paralysis are good too.
If you're hunting an electric Pokemon, put a Pokemon with static at the head of your party. This'll help ensure even more that you'll run into your chosen Pokemon (or so it is believed).
App. No. 20, the Pokeradar App, is very helpful. It will tell you how many pokemon you've chained, as well as your longest chains so far. This'll help you determine when you're ready to start resetting for shinies.
Register the Pokeradar. This'll help you out a lot.
Put your repels at the top of your item list.
At some point, stop chaining and start resetting. Most people say 40 is a safe number to start resetting, but as long as you have enough patience and repels, even 20 could work. It's all a matter of how far you're willing to go to raise your chances. A chain can break for seemingly no reason at all sometimes. It's best to be extremely cautious.
If you need a break, take one! But make sure you'll know where you are when you come back. I find it best to take breaks in the middle of a battle, or right before I reset the Pokeradar. But whatever works for you. Real time won't affect your chain, so take all the breaks you need. Just be sure to plug your DS in if you need to leave it on for a while, and putting it in sleep mode won't hurt either.
(New) While it would make since to think that increasing the chain to very high numbers would greatly increase the chance of encountering a shiny, this is not the case. The formula for chaining shows that the maximum chain number you can get is 40 before it doesn't matter how high the chain is. When the chain reaches 40, from that point onward, the chance of encountering a shiny is approximately 1/200.
And that's it! If you stick at it, you too should notice results. I've only been doing it for five days, and I already have five shinies to show for it!
- These rules, if broken, will most likely break your chain.
** I have seen it happen sometimes where your chain can "shift grass types." What I mean is, I may start out with non-glittery grass, then all of the sudden, the chain will shift to glittery grass, and it's all that appears. I've had chains successfully shift to the new type of grass and keep going. Be extra cautious if you suspect this has happened." From: http://bmgf.bulbagarden.net/f323/shiny-pokémon-pokéradar-19695/