This is probably a basic question, but I have just never asked or really thought about it...I usually record single instruments, such as guitar, bass, etc. in mono...when is it best to record in stereo? I read on here a lot about this but I guess I really don't understand when to record in mono and when to record in stereo...I feel like that kid in class asking the dumb question..hahaha...please be gentle as I am a very sensitive soul...

you never have to record in stereo.  if you mic a drumset, coustic guitar or piano with 2 mics, you can capture an accurate or exagerated stereo image.  some sources like keyboard or synth patches with panning efects must be recorded in stereo or you will lose something.   this is just the basics, i am typing on my phone

From what I've read on this it seems like instruments like guitar, bass, individual drum mic's, vocals, horns etc. are best recorded mono.

Over-heads, piano, room mic's, choir, orchestra and the like are best recorded stereo.

Of course as you know there are no rules but this is what I've learned.

Mike

It isn't dumb, but obvious.  a stereo source is recorded in stereo.  Overheads are a likely canidate, stereo keyboards, many softsynths.  Also stuff that ends up spread out as stereo can be recorded that way - string quartet, choirs, wide groups of similiar instruments.  But for most of us doing rock or jazz or pop music it is mono.  Other than OHs drums get mono, guitar amps, basses, vocals.  Other than a leslie, there are few things in a regular band that need a stereo treatment when recorded.

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Actually if your recording overheads, you'll use 2 mono tracks, not a stereo track. 

Basically if a source has one wire running out of it, its mono. 
If it has accommodation for 2 wires then it can be recorded in stereo. 
Hey, there are stereo guitars ya know! 
And there are stereo mikes, but I'd rather still keep all my tracks as mono unless it's an output of an audio playback device or some keyboards.   

Thanks guys...I guess I had it right...just making sure...good to know I have been doing things pretty much as everyone else...thanks!

The only thing I'll typically record in stereo is keyboards.
Prefer to have drum overheads as a "stereo pair" of mono tracks
If I want to adjust/process background vocals as a whole, I'll route the individual (mono) tracks to a stereo bus.

Actually Johnny's way does offer more control over where you can place things.
Front, back, left right.
When I record guitars, acoustic or even amp's I use 2 mic's on 2 mono tracks.
My next recording, I'm going to record anything that can be mono to mono.

Mike   

Main reason I do not record any mike track in stereo is I will want the option of processing it separably. Even if the mikes were a matched pair, the sound might need tweaking just a little differently on each side, say the left mike picked up way to much low tom etc.   
The other reason is I might not wish for a full stereo spread. 
The more control while mixing the better. 

Great stuff guys...thanks alot...all of this made very good sense...thanks!