Try to chain as early in the day as possible, pick sparking patches and use magnet pull.
My 3 highest chains are 137 Magnemites, 131 Castforms, and 125 Lotads.
I just wanted to share some of my chaining experience with people in this forum. I've logged in over 1000 hours of chaining between 3 games. My main game (pokemon diamond) has 960 hours and my used (pokemon pearl) has 150 hours. I also chain on my girlfriends game from time to time. As of right now I'm close to catching 600 shiny pokemon, by means of the poke radar (pokeradar) and random encounters in the wild.
I have 138 shiny pokemon videos uploaded in youtube, of most of my shinnies and the chains I caught them in. Just search for shiny pokemon Z33.
I totally disagree with the posts about the odds of finding multiple shiny (7 or more) pokemon in a chain of over 100 is impossible. It is not impossible! I've caught 17 Eevees in the same chain. I started to reset at 40 and I caught one after the other until I reached 57. I didn't want to catch anymore because I caught enough for the Eevee's set of evo's. I was also catching for my girlfriend that's why I had to catch extra. From my experience you can actually catch a shiny pokemon in any chain. It just depends on how much you want to increase your odds of finding one. In the beginning I use to reset at 30, but when I decided to reset at 40, I ended up on using a lot less repels, proving that the odds of finding a shiny is a lot higher at chain 40. I got to go...to be continued.