As a Ganondorf... DO NOT APPROACH. At least, not like any normal characters. RAR Bair is his only option for approaching (if you need to) that is generally safe, but it needs good spacing and does not hit all characters. What a Ganon main should do is bait out laggy moves and punish. Notable punishes include: every single on of his moves that you can hit, besides jab. Ganon is a powerhouse and that is his only redeemable quality, but his moves are so slow that it makes it much harder to hit opponents. You should always look to punish landings or laggy moves with a Flame Choke or Dash Attack, since those are your best options.
The center of Ganon's game is making reads, especially with moves such as Flame Choke. If you notice your opponent using the same tech-ing patterns after a Flame choke, follow them with another Flame Choke. If they tech roll in away from you, punish with a Flame Choke or a Wizard's Kick. If they tech roll behind you, punish with a Flame Choke. If they tech right away and do not roll, you can jab on some and dtilt still works, but it isn't guaranteed. If they don't tech, punish with a dtilt, or if they are using get up attacks everytime, walk away and Flame Choke them again. It's all about guessing and knowing what your opponent will do based on his or her habits while playing. This is all very match-up based, so you should look into threads on match-ups.
Keep in mind that since Ganon is incredibly slow, you need to play defensively. Let your opponent approach you, not the other way around. Don't be too frustrated by losing and don't give up on getting better. Ganondorf, while technically simple, is a very hard-to-play (effectively) character, but he can be very fun once you get the hang of him.
EDIT: Forgot to mention autocancellinng aerials. His U-AIr is great. If you U-Air right after short hopping, you'll land with almost no lag at all. It's helpful when combined with RAR, but situational nonetheless. Also, find a Ganondorf guide in the guides section of this website.
