Yea just practice 'combos' on the sandbag before your wifi games and you'll learn the timing pretty well... training mode works just as well as the sandbag but you need to try it on real people (in the wifi games that are loading while you're practicing on the sandbag) so that you realize that most of the times in which you'd like to knee someone you shouldn't try it because they'll shieldgrab or smash or FAir/NAir you. The best ways I know to land a knee on someone are:
> Do a SH approach at someone, and if they try to FSmash you, use your second jump to get away but DI back in for the Knee (best used on large characters because if you time it too late on short characters you'll get punished bad)
> On short platforms like Battlefield, you can sweetspot a lagless knee (SH) on someone's feet if they are on the platform above you (hits them if they are knocked down too; usually you want to have them be at slight diagonal forward in front of you because when you do the Knee you usually go forward)
> You can also full hop it at people on platforms above you, but it's not as safe
> Dash-attack to jump forward to knee works alright, although it is avoidable; it probably won't work on the same opponent more than twice
> I havn't gotten around to trying this yet, but if you are expecting someone to roll behind you because they are expecting you to try to Smash them, a retreating knee might hit them. There should be enough time for you to tell whether or not to throw out the knee (if you shouldn't, don't because a sweetspotted knee will give you landing lag; if they spot-dodged or shielded, they can probably punish it)
Thats about it.
Honestly, I throw out (and hit with) more Falcon Punches than Knees, because Falcon Punch has great range and is better suited for mindgames.
