FREQUENT SPELLING MISTAKES

1) PRACTICE / PRACTISE


Although both these words are pronounced the same (with final /s/ - neither with /z/), the former is the noun and the latter is the verb.


     I'd like to do some practice now.
     I'd like to practise now.


2) ADVICE / ADVISE

 Advice /s/ is the noun, and advise /z/ is the verb.

    If you wish good advice, consult an old man.

    Her friends advised her not to go out with such a quarrelsome guy.

N.B. These words do not mean warning/warn, but counsel, but counsel itself is a formal word (really literary when used as a noun) and is therefore better avoided in ordinary speech.