Season 30 of the Whoniverse, to my way of thinking of it, is best served by viewing it in a certain order.
Season 30: (2007-2008)
797 30x01 Kiss Kiss, Bang Bang [Part VIII]
This episode of Torchwood continues the story of Captain Jack shortly after the closing arc from the previous season. Some would place this episode during those episodes, but it just didn't feel right there to me; it interrupts the flow of the episodes when placed there. Here it serves as a kind of coda to that arc, and sets up the next phase of stories. This episode also serves the parent series when placed here, as it references the Doctor, who won't appear on screen for 8 more episodes.
798 30x02 Invasion of the Bane
This episode, which is basically the pilot episode of The Sarah Jane Adventures, feels like a breath of fresh air after an 8 episode, Doctor Who / Torchwood Epic story. This gives the audience a break, while introducing new characters, and again referencing the Doctor, who won't return for 7 more episodes.
799 30x03 Sleeper
800 30x04 To the Last Man
801 30x05 Meat
802 30x06 Revenge of the Slitheen, Part I
803 30x07 Revenge of the Slitheen, Part II
These episodes break up the run of Torchwood episodes, and actually give the audience more time between "Meat" & "Adam", which makes the storyline in Adam easier to buy into. Part II of this story also mentions the Doctor again, and references Rose Tyler - both of whom will return 2 episodes later. The Judoon are also referenced in these episodes; those aliens will return in the flesh in #834 30x38 "The Stolen Earth". The planet Clom is also mentioned in Part II (having previously been mentioned in "Love & Monsters"), and becomes important in #834 "The Stolen Earth" & #835 "Journey's End". The Slitheen obviously appear here as well, and will return again in episodes 828 "The Lost Boy, Part I" & 829 "The Lost Boy, Part II" before being referenced by Jack in #834 "The Stolen Earth". Nice Foreshadowing in these episodes.
804 30x08 Adam
805 30x09 Partners in Crime
806 30x10 Reset
807 30x11 The Fires of Pompeii
808 30x12 Dead Man Walking
809 30x13 Planet of the Ood
810 30x14 A Day in the Death
These last 3 episodes of Torchwood ("Reset", "Dead Man Walking" & "A Day in the Death") feature Martha Jones from Doctor Who and seem to take place a considerable amount of time before her upcoming return to Who ("The Sontaran Stratagem"), so these episodes should be viewed first. There doesn't have to be much of a gap between them (or any gap at all) because The Doctor & Donna are traveling through time. But I think it helps me as a viewer to see something between Martha's last appearance on Torchwood and her next appearance on Who.
811 30x15 Eye of the Gorgon, Part I
812 30x16 Eye of the Gorgon, Part II
As mentioned above, having these two episodes between "A Day in the Death" and "The Sontaran Stratagem" helps me (and I would think other viewers) from the time travel jet lag effect of watching them back to back when there seems to be a bit of time gap between them. But another reason for placing these episodes right here is that in "Eye of the Gorgon, Part I" Sarah Jane & Bea discuss the Sontarans of old; a nice reference to classic Doctor Who stories, as well as a creative foreshadowing of the coming Sontaran Stratagem. These are the kind of moments that can help inter-series continuity, if viewed in this order. If the shows are viewed separately it's possible and even likely that a reference like this will be forgotten, but placed just before the Sontarans return to our screen, it's a nice reminder that Sarah Jane has experienced much with the Doctor that remains relevant even now. The Sontaran reference also serves to foreshadow Sarah Jane's trouble with one of these aliens later in the season in 831 & 832 "The Last Sontaran, Parts I & II".
813 30x17 The Sontaran Stratagem [Part I]
814 30x18 The Poison Sky [Part II]
815 30x19 The Doctor's Daughter [Part III]
While these 3 consecutive Who episodes aren't widely considered a three-part story, it seems obvious to me that they are. Most sites list "The Sontaran Stratagem" / "The Poison Sky" as a two-part story followed by a standalone, but "The Poison Sky" ends with a cliffhanger that is resolved by the closing credits of "The Doctor's Daughter". I try not to separate multi-part stories.
816 30x20 Something Borrowed
A nice stand alone comedy after the drama of the previous episodes.
817 30x21 Warriors of Kudlak, Part I
818 30x22 Warriors of Kudlak, Part II
Multi-Part stories are kept together.
819 30x23 From Out of the Rain
820 30x24 The Unicorn and the Wasp
821 30x25 Adrift
822 30x26 Silence in the Library [Part I]
823 30x27 Forest of the Dead [Part II]
Multi-Part stories are kept together.
824 30x28
Whatever Happened To Sarah Jane?
Part I
825 30x29 Whatever Happened To Sarah Jane?
Part II
These episodes actually set up certain sequel elements in the first part of the Doctor Who 3 Part Finale, "Turn Left". And though they don't need to be set directly prior to that episode, they should be seen before it. The Trickster introduced here is referenced in "Turn Left". And here, the Trickster references both his interest in tangling with The Doctor (setting up "Turn Left") but also mentions the coming Darkness as well (which is a key element in 833 "Turn Left", 834 "The Stolen Earth" & 834 "Journey's End". Fantastic set up, though the Trickster isn't named on screen in this episode, though he is in the closing credits.
826 30x30
Fragments
[Part I]
827 30x31 Exit wounds
[Part II]
828 30x32 The Lost Boy, Part I
829 30x33 The Lost Boy, Part II
Multi-Part stories are kept together.
The events of "The Lost Boy, Part II" (the season 1 finale of The Sarah Jane Adventures) and "Exit Wounds" (the season 2 finale of Torchwood) are referenced directly by dialogue and actions seen in "The Stolen Earth", and by more subtle dialogue in "Turn Left" - so these episodes have to be seen first to enjoy the pay off of those remarks and actions.
The Torchwood episodes were listed first as the events of the finale seem to take place a bit before the Who finale. "The Lost Boy, Parts I & II" seems to be set fairly soon after the previous Sarah Jane installments. The episodes don't pick up exactly where they left off though, so having the Torchwood 2 part finale set between them wasn't my first choice, but then I realized that the episodes actually take place in the course of 1 single day, so that was settled.
Also, this 6 episode gap with no appearances of the Doctor is lessened to some degree by the Doctor being mentioned in "Whatever Happened To Sarah Jane, Part II", "Fragments [Part I]", & "The Lost Boy, Part I". There are also a multitude of references to various Doctor Who episodes.
830 30x34 Midnight
A nice little stand alone episode to break up the epics, and give us a taste of The Doctor, who we haven't seen in 6 episodes.
831 30x35 The Last Sontaran, Part I
832 30x36 The Last Sontaran, Part II
The first 2 episodes of Sarah Jane's 2nd Series, these episodes serve as a direct sequel to the earlier Doctor Who episode "The Poison Sky [Part II]"; reminding us of the events from those episodes, which will be referenced again in the next installment. Also, The Trickster character from Sarah Jane's "Whatever Happened To Sarah Jane, Parts I & II" (who is key to the following episode of Who) is named on screen here, making it vital that these episodes be viewed before "Turn Left [Part I]".
"The Last Sontaran" features a nice bookend to the 1st Season of Sarah Jane as main characters Maria & Alan Jackson, who arrived in the first episode ("Invasion of the Bane"), leave the series here. Some would likely note that as the first episodes of Season 2 they also bookmarked that season as well as these episodes feature the first appearance of the Sontaran Kaagh, who's final appearance is in the 2nd Season Finale, but to my way of thinking of things, those episodes ("Enemy of the Bane") aren't the finale at all and therefore no bookend involving the character is present or required.
The majority of events of these episodes take place before the huge Who finale that follows, yet the '6 weeks later' epilogue to "The Last Sontaran, Part II" - likely takes place after "Journey's End [Part III]". In dialogue in "The Stolen Earth", Luke tells Sarah Jane that Maria and her dad are in Cornwall; just the kind of trip that those departing for the United States might take before leaving that side of the pond. These episodes also reference almost every previous adventure, while not mentioning the Daleks at all - so it seems likely that they haven't encountered them yet.
833 30x37 Turn Left [Part I]
834 30x38 The Stolen Earth [Part II]
835 30x39 Journey's End [Part III]
The big payoff for the season, and the entire run of new Who, Sarah Jane & Torchwood - these episodes serve as a finale to all 3 shows, giving us a big bang finale before 2 of the shows all but hibernate in the coming Season 31. In Season 31 Sarah Jane continues as usual (covering 1.5 Seasons of her show; 1.5 years of her life) while Torchwood is reduced to a single 5 part story, and Doctor Who is relegated to a series of specials before returning to form (albeit a new form) in the following season. As it stands, Season 30 of the Whoniverse (my favorite so far) had 3 very different tv series with a number of episodes each equal to the others and all of them serving to strengthen the storylines of one another. How cool is that?
Back to the Doctor Whoniverse Episode Guide