Hi, I did the AQA board so not sure if all the advice applies but
for spanish learn as much general vocab as you can, you'll need it
you can use quizlet and brainscape to do this
learn some idioms, phrases and some really native expressions to really stand out, it's what boosted my speaking and writing marks
try to watch some spanish shows or music etc for speaking and see what words you can interpret and pick out : it helped me get used to the pace and style of the listening exams
for grammar use LANGUAGE GYM!!!! YOUR BEST FRIEND
learn how to conjugate properly- dont be lazy about it