well first its better if the pokemons hp is either in low yellow or red now its easier to catch now if you want an even better chance at catching the pokemon either paralze freeze sleep, burn or posion ( except burn and posion lower its life even more so becarefull the best are paralzye sleep and freeze) then throw a ball that fits the loactaion or time or just any ball will work

Dusk ball better at night or in caves
Quick better beginning of battle
Timer better longer the battle
net better 4 bugs and water
nest better for weaker pokemon
Ultra better than great ball better chance anyways(than a greatball)
Greatball better chaces of catching than a pokeball
Pokeball regular catch rate
Master automattically catchs pokemon

(note there are more balls to see how well the ball works read its description)

So in a recap weaken pokemon either paralyze sleep or freeze the pokemon While weaking the pokemon unless u use thunder wave or static then TRY and use a ball that is best suited for the desired pokemon
*note for legendaries its best 2 save b4 encountering