It has been a long time since I’ve written a commonly confused words post, so I figured it was time for another one.
None of us are immune to being tripped up now and again, even those of us who consider ourselves good at spelling. Sometimes even words we know how to spell might slip through the net. Do any of these errors crop up in your work? Do you notice them when you are redrafting? Do your beta readers point them out, your proofreader, your editor, or heaven forbid, your readers?

Altogether means completely, but all together means everyone in the same place.
Censor can mean to examine and suppress, but sensor is a measurement device.
Clamber can mean to get oneself out of something, but clamour (clamor) is a loud noise.
I might have a discerning palate, but I unloaded a pallet of boxes last night
Bells peal, but I have to take the orange peel off before eating the orange.
Someone might have an annoying tic in their eye, but they would avoid being bitten by ticks, and they would receive a tick and a gold star from the teacher for doing well in class.
You take your cue from those who know what they are doing, but you would stand in a queue at the post office (I realise that in the US people stand in lines!) And yes, it’s a snooker cue.
You could challenge me to a duel, but you would say James has dual nationality.
I couldn’t give a whit about football (not one iota!) but his brand of sarcasm and wit appealed to me.
You’d watch someone like a hawk and you’d hawk your wares at a market, but you might sip a nice glass of German hock
Someone might require you to come to their aid, but the prime minister’s aide was present at the conference.
You lose some weight, but your clothes are loose on you because of it.
You might pour yourself a nice glass of wine at the end of a hard day’s work, but students pore over their homework each night
You might bear a child, but the woman’s face was bare of makeup.
The principal reason we are here is to write, but I might not do something because it goes against my principles.
You might buy some stationery to put in your office supply cabinet, but your car was stationary when it was hit by the bus.
Sven was loath (reluctant) to wear his good clothes for work, but I loathe (hate) when people don’t say thank you.
Practise your English, but I visited the new doctor’s practice in town (NB: practise does not apply to US English)
The apartment I went to see was dingy (gloomy), but I went out in a dinghy on Lake Windermere.
I might invite you to my gaff for a party, but it would be a real gaffe to unintentionally invite all of my friends except one.

 
There are many more. I hope that has helped a little.
My suggestion is make a list of the words you know you confuse or are prone to mix up and continue to build upon it. Use it as a crib sheet when you are writing and redrafting. You can’t go far wrong!

Next time: italics