@matmanx1
I'm confident in my understanding of the mechanics, but as far as competitive execution there are others you might want to consider a little more heavily. Especially for the last question, which I don't really have an answer for.
For one, check out the first part of this video focused on jumping and boosting. There are several of these EXVS tutorials around, I think Donkey even posted one several pages ago, but this one is more recent and shows you the (default) buttons and directional inputs for what they're doing, so you don't have to understand Japanese to at least get the basics of what they're talking about.
http://www.mmcafe.com/nico.html#http://www.nicovideo.jp/watch/sm16472500
I saw on the gamefaqs movelist guide where the author was talking about being able to tack on a jump to an aerial boost dash to cover ground quicker. Does anyone know what I'm talking about?
The first segment in that video relates directly to this. It might not cover ground 'quicker', but it conserves your boost bar by letting you travel a little farther using your BD momentum. You do it by doing the BD, then letting go of the lever/direction and tapping Jump again. You'll notice you still go forward a little bit, but you don't use any more of your boost gauge. Useful.
The second part of the same segment shows that if you press a direction again during the last jump, you travel even further. Then it compares the distance between the two.
Second question: Should I be on the same target as my partner at the start of the match or should I purposely pick the one he's not on? I always assumed that ganging up on one unit at the start would be more effective but maybe that's not the case?
I think as we start to form some better teamwork, this kind of thing will be more intuitive. Some of us have certain combos that we've gotten used to doing, but if the partner interferes at all it can actually reduce the damage of the combo considerably. I think in general, if your partner is already actually attacking someone, you're better off watching his back to make sure he isn't interrupted than trying to contribute. On the other hand, if the target is attacking your partner you know to try and interrupt that. I believe the term for interrupting a combo being performed is 'cutting'.
How often do you guys target change? I feel like I'm getting hit quite often by attacks I never saw coming. My thought is the target change will help me keep tabs on both opponents better but obviously you don't want to interrupt a combo or attack string to do it.
On the contrary, as soon as you start a melee string--assuming you're not going to step cancel--you can switch targets and still complete the string. Similarly if you have any one-shot ranged attacks, you can switch as soon as you fire it too. This way you can hit the guy in front of you while watching your own back (and step-dodge accordingly) or planning what you'll do next.
Even if you have no boost left, you can follow up your melee string with a charge attack you might have been holding. If you released it on the guy you just smacked down, it'll have no effect since he's 'down' (yellow lock). But if you switched targets, you might have a chance of hitting the other guy.
I got no tips on 'getting in'.