I wish to improve upon Corey's answer. It is a decent answer, but I must point something out.
If you want to catch Entei/Raiku, Mean Look, and Spore is a must. BUT If you do not use Spore IMMEDIATELY after using mean look, they WILL use roar. Forcing your pokemon to run, ending the battle. So having a Smeargle with Taunt in the 4th moveslot is equally as helpful, if you don't have access to spore. But it is just as temporary as Spore, (2- 5 turns), so you need to have something that can attack hard, and fast. Assuming your Smeargle is at least Lv.50, but I'd recommend at least level 65, due to it's appalling terrible stats. (The Lengendary dogs at LV.40) That way the attack stat of Smeargle is good enough to cut it's HP down to 1 with False Swipe. I recommend using either Silk Scarf, or Metronome as a held item (to power up False Swipe). For where they can be acquired, see your games walk through.