Please feel free to do some ranting of your own in the comments--at me, at the show, at the weather. (My strawberries keep going rotten before they ripen, because of all the rain. So very frustrating.) I promise to at least feign interest and not to laugh.
1. Paid more attention to detail and character backstories
One of the things I loved about the early seasons of SG-1 was how believable most of the military stuff (including character reactions in combat situations) was. That made me more willing to buy into the crazier alien stuff and the handwaving when necessary. What might the equivalent look like on SGA? Take Sheppard's hair as an example: something that could have been very effect would have been to give him a regulation haircut in the pilot, and then let it grow out over the course of the season as a subtle way to show both the passing of time and the process of them slowly going native (so to speak). Would have driven the continuity people crazy, but also would have been worth it. Then, if they wanted to leave it long for the rest of the show, they would have earned it up front. Instead, he's simply inexplicably non-regulation.
Another thing would be to lay out skill sets and duties for all the characters from the beginning--have them adapt and learn new things, sure, but don't let them suddenly lose skills they displayed in the previous episode. If a character can fight off 5 monsters in one instance or dial a gate remotely with a broken ipod and a screwdriver, they should be able to do so in subsequent instances. If not, make clear why not. Similarly, each encounter in the field or attack on Atlantis should have policies developed in response. Midway is an excellent example of how not to do this: no irises on the Midway gates, no way to completely lockout a non-human, no effective defenses (except locked doors) within the SGC--and this after, what, 14 years of fighting aliens?
...Okay, so that's a pet peeve of mine.
2. Had clear story arcs within each season and over the course of the show
Burn Notice is a good example of this, or the last set of episodes in the first season of NCIS. In each case, each episode has two plots: the main story, which stands on its own and ends before the credits start rolling, and bits of the larger story arc that fit in around the edges. Events in one episode have repercussions in following episodes.
This has two effects. It discourages anything too over-the-top, since the writers will have to work around it in subsequent episodes, and it also gives the viewers a reason to tune in next week. The trick is balancing the episode's story against the season's story, so that the one doesn't obliterate the other. And also not doing too much damage to the main characters, since they'll be wearing the bandages for at least a little while. No magically-healed broken legs, unless someone at least throws in a comment about Ancient healing devices or something.
3. Narrowed the characters' skill-sets a little
Physicist does not equal hacker/programmer/engineer.
Also, American marines are damn good at what they do. No fair treating them like redshirts. (Although I suppose that's actually widening the characters' skill-sets to include 'not automatically dying'.)
Yeah, it looks pretty, but it's also absolutely ridiculous.
4. Played with the whole multi-culture, multi-lingual expedition thing a bit more
Did they actually do anything with this beyond sticking flags on peoples' shoulders and having a couple of main characters with accents?
5. Made it just a little bit more about an expedition off by themselves in another galaxy
It pretty quickly turned into "SG-1, round 2". Me, I would have kept the ability to send messages, and maybe a one-way relief mission (yearly supply dumps, at most), but then kept it at that. Made it more about the expedition improvising and forming trading relationships and being off in the wild frontier by themselves. That's what was new and different and interesting, not the space vampires or the replicators 2.0.