Okay, for both of these things you are going to want to be reading your opponent at all times. Do your best to analyze their playstyle, find where they are predictable, and exploit it. Most players tend to have habits -- whether it be their combos, their techs, their ledgeguarding, their movements, it can be anything. Just keep your eyes open and your head in the game.
Mind games are all up to you... they can't really be "taught." Of course, there are fundamental mind games that are very basic like dashing in for an attack and shielding or wavedashing back, empty short hops, jumping in for an aerial and then jumping away at the last second, the staredown(facing your opponent not moving at all), dash dancing to some extent can be used, etc. However, this is one of the areas where it's really up to you to get creative. Mind games tend to be unique to the player and their playstyle, which is what makes them mind games. Be creative and be unexpected.
As for DI, in my opinion, that's mostly practice. Work on SDI as well, it's very important. Reading your opponent can also be extremely beneficial to your DI so you can DI out of a throw or a combo. Pay attention to your opponent and be prepared to DI/SDI at all times.
