quote marks - mismatched, or improperly nested, or improper use of single or double quotes.
semicolons - and other end of statement or end of line terminators
parenthesis or brackets - mismatched, improperly nested or wrong type used
0's or 1's - not understanding if the counting, increment or iteration of a value was zero based or one based.
typos - e.g.- typing 'id' as a var name when we meant 'iid'.
Maybe others will add to this list of common coding errors.