I'm a college student and our class's current project is to make a radio drama.
I suppose I should be weighing in on this one. So, what do you have as resources? What kind of college, for a start - I went to a scientific and technological college, so we always had a wide selection of technical volunteers, but were drastically short of performance talent, while my nephew, who teaches drama, has the inverse problem (and used to cadge sound effects from me, until I copied him over several tens of thousand and told him to list and label them himself). What are you using as recording gear - I assume computer based, though I'd be quite happy to lend you a Revox and some single-sided razorblades. Computers are ubiquitous, audio editing/manipulation software is cheap (often free) and widely available, and plug ins and sonic modulators are easily found (just ask your musician - there's always one).
Performers.
How many do you have who're flexible and convincing, for the lead rôles? Oh, if this were a drama college there'd be people fighting for the parts, but it's more likely you're looking at your more gifted thespians doubling and even more on characters. This can be a very important factor in choosing a piece to record, or adapt for recording.
Narrator
Do we need one? Can dialogue eliminate explanations from a godlike overseer?
Recording Domain
Where are you expecting to do the recording? Hall of residence, students union theatre, classroom, bar? You're unlikely to have decent soundproofing and acoustics, because these are inherently expensive, so choosing a piece where either additional ambient sound masks the imperfections of the available space, or a claustrophobic enclosed imagined environment can make working in a closet viable (first man to the moon stories encourage this viewpoint, but there have already been men on the moon, so they are less appealing than in 1953, when 'Journey into Space' was transmitted.) Multimiking, each performer individually captured, reduces the criticality of the acoustic.
Length.
I'm assuming we're only aiming for aa adapted short story, maybe a quarter, half an hour, though I haven't yet asked. Whatever, the combined time rehearsing, recording, editing, overdubbing, replacing bits that sounded all right while you were recording them, hunting out sound effects and music cues and finally mixing is, while very satisfying, many, many times longer than the final edited version. So start well early, or go for very short pieces. Fortunately SF has a vast selection of excellent short stories.
Listen
If you are writing a book, you read a lot - for recording an audio only version, listen to what a lot of other people have been doing and, in addition to the theatre, listen to bits of audiobooks. The technique's not identical, but closely related, as the desired result is the same.
Special Effects
Reverberation, echo, voice distortion and modulation are all standard SF/horror additions - and all available on the cheap and cheerful.
Sound effects
can be subdivided into punctual effects (breaking glass, gunshot, furniture scrapes, robot footsteps) occasional (wind gusts, passing traffic, wolf howls), ambient (which can be retorts bubbling in a laboratory as well as pumps in a spacerocket or whistling wind round an observatory) or weird, generally attention grabbing, and frequently more music than signifying any particular action or information. Recording, editing and preparing them yourself is great fun, or you can download them, or buy them ready indexed and cut. Lacking the visual clues,
Music
Hmm. Obviously, if the music can be composed, performed and recorded specially for the piece this removes a number of potential hurdles to its use, even if the absolute quality is not up to the standard that can be pirated without too much effort (getting official permission to use existing recorded music is work - I've had to do it in the past, and even wallpaper music distributors fight like mink to get a few pence of performing rights). But generally these pieces work so much more fluidly with some music - it's not like audiobooks where it's totally a question of choice.
Recording technique
Are you going to record '50s style, with all the performers gathered round a microphone with texts on music stands, or twenty-first century, multitrack and editing together different takes from different performers? The intereaction method tends to give more life in the performances, while the Lego technique means you can prepare scenes separately, record people who happen to be there, pitch-shift voices or sound effects and do fifteen takes of one phrase before you can do it without laughing.
Style
Radio theatre has been done dead seriously, or totally ridiculously (as with Hitchiker's guide), thriller, moral story, utopia or dystopia - SF gives you the elbow room. If you can't raise everyone's enthusiasm for a particular project, at least you should be able to get a solid majority, because this is hard work to do well.
And it's not worth doing it mediocrely.
If there is anything else in which I can exude my erudition (and probably be intensely annoying) don't hesitate to PM - no, we don't Personally Message each other any more, do we? We conversation) well, get in touch.