I would definitely recommend going with a guide instead of doing it on your own. The guides know the park well and will know where to look for game. I did the Kruger National Park 2 years ago and my guide was able to see an elephant on a hill that was over 3km away. Absolutely insane!
Also try and get up as early as you can. I was beginning safaris at 6am and its well worth getting up earlier as you see so much more. I didn't see all of the Big 5 though, which was really disappointing.