Quick Balls are the best on the first turn of the battle; on turns 2-9 Dusk Balls are the best (provided you're doing the capturing at night); and on turn 10 onwards Timer Balls are the best.
You should also try to lower its HP (the move False Swipe is the best way to do that without risking accidentally fainting it) and put it to sleep. If you don't have a Pokémon that can put it to sleep, you can also paralyze it, but sleep is a lot better.
Here's a calculator you can use to determine your chances in different situations.
