I get confused with b's and c's, because those are rare letters in Finnish language.
An example: I was writing a letter, and I ended up checking these three words in my dictionary, because I wrote:
"No more crab about this..."
" I crabbed my pen..."
This is not the only one I must check often.
Other letters, that confuse me a lot, are q and g - q is not used in Finnish at all... quiet, guiet, quite, guide...
Do I have to write them all down on a piece of paper or how on earth I start to remember these difficult, same-looking words!
I don't think there's a simple answer to this; I see advanced Japanese students confusing l & r in writing. However, having identified the problem, I think that building up and keeping a list of words would be a good idea.