"THEN" and "THAN"

"Then" relates to time. "Than" is used for comparison. Ex.: First, we'll have lunch, and then we'll go for a walk. He is more experienced than I am.

"ACCEPT" and "EXCEPT"

"Accept" means to receive or agree to something. "Except" means to exclude or leave out. Ex.: Please accept our apologies. Everyone is invited, except for Tom.