Ok, the easy fixes first:
You seem to like to attack. A lot. Curb the enthusiasm to an extent because if you're always attacking in the direction of the enemy, you can be predicted. A little restraint goes a long way in terms of being so predictable.
Recognize the patterns of your enemy. You should usually be doing one of two things: watching your opponent while moving around, or attacking/moving in for an attack. If you're always attacking, you can't be dodging the fox and punishing the missed attack. For lower level play (no offense, I just mean w/o learning to wavedash etc.) you can start by watching them run up to you only to have you spot dodge or roll, and then attack them while they're finishing the attack.
If you're not attacking and don't know what to do, move around. Dash dancing is one of the easiest ways to effectively do this, and it's just a matter of timing.
Make use of a couple of different approaches. A few good ones are running up and grabbing OR dash attacking at a farther distance (like bat distance), or instead of just jumping and doing an aerial, pause for a little in the air by double jumping and immediately doing the same aerial attack you would have done. for example: if you would jump and hit with a down air (the stomp), double jump and then stomp some of the time, because if your brother expects it sooner, you may hit with the double jump then stomp.
DJC (or double jump cancelling) is the name for what I described above. If you do an attack too soon in Ness's second jump, he'll stop moving upward. This can be used for low aerials, or to manipulate the timing of attacks.
I respect that casual play has it's place, and the stuff I just described is all within the realm of anyone's ability to do. They're just a few steps you can take to make you game more solid without spending time learning advanced techniques. Of course if you want to learn them, I whole-heartedly endorse their use.
If you have any questions at all, feel free to ask. Any one new to the Ness boards, welcome! And happy New Year!
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