I heard from the amorphous, anonymous "they" that publishers and agents think less of you if you ask they recycle the manuscript and only send a #10 SASE. Something about not caring enough about your own work to want the 'script back; consequently, why should they care about it? This alleged advice could be pre-home laserjet paper by the ream at Costco's, or it could be crazy yak droppings, so I turn to you, Miss Snark: is there the slightest shred of truth to this?
Wait, I'm supposed to think about you?
Trust me, I don't think about you as a person at all; not one little bit.
You are the sum total of your font and paper choice.
I read the query. I respond.
If you include anything other than a #10 SASE in your query I hiss "nitwit"; Killer Yapp barks and the caravan rolls on.
I couldn't tell you one single name of a person who's queried me if I haven't asked for a partial or full ms from them.
Now, if you send me a partial or full and you include a BF envelope to send it back, then I do think about you--I think you ARE a nitwit, cause the letter I sent asking for this stuff says "#10 only".
As for editors, if you're sending unsolicited manuscripts to them, stop.
If you're sending solicited manuscripts, you can call and ask. Most places now will give you directions on their web site.
Editors care about good writing, and sales potential. And shoes.