Use your master ball.
a master ball or you can make it go to sleep and make it have low health and catch it with a ultra ball
The dusk ball has a higher catch rate in darker areas, like the cave Azelf is found in. It is also slightly cheaper than the ultra ball, which yeilds similar results. Of course, if you choose to use your Masterball, it will work without fail.
Azelf is found in the Sinnoh Region, in one of the three caves in the middle of the three lakes. (Pokemon Diamond and Pearl). You can catch azelf after you catch the Pokemon Dialga or Palkia. It depends on the type of Pokemon game you have Pearl for Palkia and Diamond for Dialga.It would be best to catch Azelf with an Ultra ball. But if you havent used your master ball yet u can catch Azelf with that. Use Kricketune's false swipe, the use luxray's thunderwave to paralyze it. It took about 10 dusk balls.
Any.
azelf is at route 23
ultra bal
You can't catch Azelf in Pokemon Heart Gold. Sorry! But you can catch it in Diamond, Pearl or Platinum. Hope this helps!
Yes. Just lower its HP as much as you can (paralyze it or put it to sleep, if possible) and attempt to catch it using Ultra Balls.
You can use any, but the best to use is the Master Ball (if you still have it), or Ultra Balls when it is extremely weakened.
Of course, the best pokeball to catch any pokemon is a master ball, but if you used it on dialga, you could put it asleep and then get its hp red and use an ultra ball
After you catch dialga you go to Valor Lake and use surf across it. Then you go in the cavern and azelf in inside it.