I’ve been trying to do this trick the moment I could do a split bottom, about a month ago. Now I can do eli-hops, and boomerang, but I still can’t do the boingy boing. Any tips?
Try to look at the boinging from sideways, not directly infront of you. Swing it forward for the first bounce, then bounce it back and forth using momentum. When it is coming back, pull up. When going away from center, pull down.
The yoyo just bounces up and down… no lateral motion
For the first bounce, you swing it forward. Then, keep the motion going. Its hard to explain.
i had they same problem where the yoyo just jugged up and down! if u try to kinda shoot its across for the first boing then just move ur finger up n down it carries on going forwards n backwards! its difficult to explain! also i found it help if i used a heavier yoyo! dunno what u have!
Nothing right now 
I’ve the worst luck. I lost my panda, broke my monkey’s bearing (shield was dented) and I’m getting my DM ;D ;D ;D 
Something good
when you get into the trick you need to use the momentum for the first boing like they said. after that try different speeds with your throwhand finger. i worked on it for a while and just recently figured it out. i was just trying it one night with different speeds and all of a sudden i could just feel it work. once you feel it one time you will have no problem with it.
it took me acouple weeks to get the feeling. When i first learned i justc oulden’t get it. I wasn’t bouncing it too much and would do bounce wait, bounce bounce, DANG!
Do big up and down motions. Just keep practicing. I practiced by doing putting the string over my nonthrow hand and bobbed my throwhand back and forth and the yoyo would do the same. So i tried it on the boingy boing and worked. But it was still sloppy.
I practiced and i got it perfect.
Practice makes perfect. Am i right?
Just practice! 
~Steven