How do you play Mass Effect 1 missions?

I've done every combination, even collecting Liara last of all. I like experimenting but now I'd say that the classic Feros/Therum, then Noveria/Virmire is the best. It makes more sense storywise and the difficulty scales well.

I don't have a specific order, I switch up most of the time. It's great to see new content like leaving Therum for last.
If I want certain things, like taking Liara to the Benezia fight, then I recruit her early accordingly. If I don't want to shoot Jeong on Feros I wait until I can persuade him. Things like these are what determine my order in any of my runs. I even did the Virmire mission pre-Noveria in one of my runs for story purposes with my Shepard.

Generally I like doing Feros first though because you can level up plenty and it's probably the easiest mission for me.

Therum
Bunch of fucking side quests
Feros
Bunch of fucking side quests
Noveria
Bunch of fucking side quests
Virmire
Bunch of fucking side quests
Ilos

I usually follow this order ...

* Citadel
* Therum
* Noveria
* Feros
* Virmire

During or between the main plot worlds I do as many side quests as I can find.

I switch up the order quite a bit. but my "canon" Shepard goes to Feros first, as this seems the most urgent affair. After all, Udina/Anderson tell you that they were under Attack when they lost contact.
Afterwards it's Therum since we are in the Artemis Tau cluster anyway to look for Kahokus' missing marines (and for the meta reason to pick up Liara).
Technically, since after your second main mission, you get the council's call about the STG team, which also seems to be in serious trouble, Shepard really should go to Virmire next in pure role play terms. However, because I think Virmire is a) one of the coolest missions and b ) the Sovereign reveal is better suited to come just before the end game, I do tend to go to Novaria first. It would be great to have a mod to opstpone the council's Virmire call to happen only after the third main mission actually.
Well, that's it, After Novaria, it's Virmire and then the end game. I do also finish up all the side missions before Virmire, so for me, Virmire is actually kind of part of the finale already (and who still wants to do side stuff after stealing the Normandy and having that super urgent mission to go to Ilos?).

In a playthrough starting with a new Shepard, it's my persuasion plan that sets the order... First question, do I want to be able to persuade Jeong? Do I want to be able to talk Wrex down? Leveling on any difficulty is no longer an issue for me. I can do any of the main missions with a low-level Shepard on Insanity quite easily since the spawns are completely predictable, I have the cover completely memorized and have developed pretty much foolproof combat game plans such that I can use any of the weapons and or skills to do the job.

Obviously, with a NG+ game, I can do them in any order the game allows since I'll have sufficient charm and intimidate points right at the start to handle any of the situations in the game... So, then, I randomly mix it up... maybe even by rolling a set of dice.

My preferred sequence is:
Feros
Therum
Noveria
(BdtS)
Virmire

And doing about two to three clusters worth of side missions in between each main mission.
That way i have a 100% playthrough, doing at most 10 side missions in direct consecution. And the entire end run is from Virmire onward extremely action packed.

Due to Feros being under attack from the very beginning it's the most urgent (why is the normandy the only ship to get there?!), and doing Therum after Noveria feels weird when ME3 squaddies mention Liara beeing there....

IIRC my very first playthrough was Noveria (The Galaxy's Techlab: Interesting ), Feros, Virmire, and at the very end Therum.

LoL So that is how it should be done, I always wondered about that.