1) Do/due - I make this mistake all the time. You can see it frequently in my blog. "You'll have to make due", I'll say. *Buzzer noise* Nope, it's make do. D'oh.
Make do means you can get along without something.
Due means something owed, or something proper.
2) Foreward/forward - Separated by a wee 'e', these two words have very different meanings.
Foreward - an introduction or notes before a document.
Forward - to go ahead, to move, at the front.
3) Horde/hoard - A horde we can hoard. Hopefully of nekkid fellows.
Horde - A large group, troop, or tribe.
Hoard - To accumulate.
4) Troop/troupe - Aha, got you, didn't I? I used troop in the example above.
Troop - A group of people in the military or police.
Troupe - Typically a theatrical or musical group.
5) Discreet/discrete - Um, I got nothin' here. Just...stop using them wrong, okay?
Discreet - To be secretive, not attract attention to.
Discrete - Distinct, separate.
Lightning/lightening - I always, always without fail $%&@ this one up.
Lightning - That crackly electric stuff that comes out of the sky.
Lightening - The opposite of making something dark or heavy.
Check your manuscripts, kids. Get those words right. Your editors will thank you. Another bonus round, I screwed up cow's udder with utter. My editor caught it and probably shook her head. I was so ashamed.
It's Friday, go, be, do.