Children of the Gods (1) - S1-E1
Corrected entry: When Apophis first enters SGC at the beginning, the worm hole shuts down. Then the fight between the SGC personnel and the Jaffa takes place. The scene then switches to some other part of the complex and back again. Suddenly there is an outgoing wormhole established. It is made clear throughout the show, that only very few aliens like the Asgard or The Nox can just establish a wormhole by waving the hand. Earth neither has a DHD (which is known to Apophis) nor does Apophis have access to the gate controls or was there enough time for the Jaffa to dial the gate by hand. Even assuming the scene switches giving enough time to enter the control room, the Jaffa can not be familiar with earth technology as to know how to initiate a dialing sequence on the computer.
Children of the Gods (1) - S1-E1
Corrected entry: When SG-1 appear on Chulak, they have ice on their face. In the rest of the episodes, they don't. Also, Major Samuels uses a radio to say "Close the iris. Close the iris." This is never seen again.
Correction: Carter mentions in the series that the reason they have ice on their faces and why they fall out of the stargate is because they haven't compensated for stellar drift. Once they worked that out, it's a smooth ride through the stargate. As for the Major Samuels thing, He left the SGC after the episode, and they changed procedure.
Children of the Gods (1) - S1-E1
Corrected entry: Right at the start when the Goa'uld come through the stargate they leave back through the stargate after the firefight... with the dialing computers in another room not directly connected to the gate room. And of course they wouldn't know anything about computers. The only person who probably could have ordered the stargate to be opened is Hammond, but it is active even before Hammond meets the Goa'uld, so that leaves him out.
Correction: We see in later episodes that a Goa'uld can fire up the Stargate with a ribbon device.
Correction: It is later shown that a Goa'uld ribbon device can be used to power/dial a stargate, and in the movie continuum there is a device that can itself dial a stargate, in either case it would be possible.