For those having problems with practice/practise, I sometimes stumble over that distinction, as both have, effectively, the same pronunciation. So there is no guide to the correct spelling.
I only remember by comparison with advice/advise.
I may offer you advice (noun), or, I may advise (verb) you.
I may advise you on current practice (noun), or I may tell you to practise (verb) what you preach.

Of course, due to the lack of distinction in the pronunciation, if I am reading something with practice/practise in it I will usually just read it in the context given, and not even notice whether it is correctly spelled.

Cheers
Nigel