Make the films faithful to Lucas's backstory as it was when he finished the original trilogy, and faithful to the original spirit of star wars. So Anakin would probably be teens or adult when he's discovered (by Kenobi!) and in his 30s or 40s when he turns dark. I bet the battle droid nonsense was invented by Lucas in the 90s to make his films more kid-friendly (ie toothless, like Han shooting second), so dump that. The Jedi would have been less of a bunch of idiots had Lucas made the films faithful to the original spirit of Star Wars. There should be minimum use of cgi, because ILM can't seem to get CGI right (judging by the prequels and the SE).
People in the films should be generally less pretentious and false. I get that the prequels are set in a more decadent era, but they really overdo making people come off fake. Yoda should be Kenobi's master and mentor. It should be Kenobi's decision to train Anakin. Fighting in the clone wars should basically be a good thing, not a sign that the jedi are corrupt (because that's the impression we got in ANH and I bet the corrupt thing was invented later). Anakin should be a good guy who went bad, not a wanker who became even more of a wanker. My god, please no Yoda imitating a fly. Do Palpatine like he was done in ROTJ, not like the horrible ROTS overacting. Have some emotional depth in the films, please.
Boba Fett should not appear. At least not while he's just out of diapers. Get Marcia to help out, because she seems to be a good influence. Chewie shouldn't appear and be best buds with Yoda. Anakin shouldn't build C3PO. The death star shouldn't be part of it. Vader shouldn't be with Tarkin at the end. Maybe make Owen Kenobi's brother. Cut the silliness and dumb comedy. Vader shouldn't go "Noooo!" like a strangled chicken when he's just been reconstructed. No idiotic drawn-out fight scenes that have no feeling and bad acting and overdone thinderous music and overdone cgi backgrounds. If there's a Mace Windu, don't make him such a pain. Don't have Yoda be a pompous ass who goes in for macho posing -keep him faithful to the ROTJ/ESB portrayal. And use a fucking puppet -one that looks something like the old one -why is that so fucking hard?
No need for Jabba to appear and if he has to appear, don't make come off like a stoned cartoon. No podrace torture, thank you very much. No cartoon characters. Greedo or his dad doesn't have to appear. The Star wars universe is not one tiny neighbourhood -everybody doesn't have to know everybody. Anakin doesn't have to be an immaculate conception, for fuck's sake and cut the prophecy bull or that nonsense about how Anakin is the most powerful person in the force, ever. I'll bet you none of that was in the original story. Now Lucas has to retcon about Anakin's force power being crippled when he goes all bionic in ROTS to explain why Vader doesn't measure up to Palpatine's force power.
I'm just splitting stuff up into paragraphs randomly here, so it isn't one long block of text. Really, I could go on for ever on this topic. There's so much wrong with the prequels. For god's sake, don't cast Hayden Christensen as Anakin. Ok, that'll do for now.