When writing I find that I have a problem keeping these two words straight. I consult the dictionary often to remind myself which is the proper one to use.
According to my Webster's I'm not the only one finding difficulty when using them.
The confusion of the verbs affect and effect is not only quite common but has a long history. Both words came into use in the 1400's and have been a source of confusion from day one.
Here's my observation of the two words:
Affect can have "ed" on the end but effect cannot.
Affect is a form of the word affection and has to do with emotion. Effect has to do with appearance and movable property or goods.
Her tears were purely for effect.
The sight affected her to tears.
I hope that this will have an effect on your writing as well as mine. :0)