Catch a pokemon that knows mean look, now make sure it is faster, and open with that. Entei cannot escape, now, switch to a pokemon that can put him to sleep and keep him that way. Switch to scizor (if you have him that is) and false swipe him down to 1hp. Catch him. Celebrate.
I cant remember which pokemon is GSC has mean look, if you can get misdreavus in GSC use her, she has it, otherwise I dont know.
Good luck.
EDIT: I have not done this in a year or two. I cant remember if it works or not.