Maths - practice little and often starting as soon as you return to school. Use spaced repetition. Leave past papers until nearer to exams and sit in timed conditions then mark, revise gaps, repeat. Keep up with work as difficult to catch up if you fall behind.
English - read quality newspaper opinion pieces as often as you can, try to understand and spot the techniques used. Practice ruae, this will help with ruae and Scottish text. I found the revision guides helpful for this. Write good critical essay plans as soon as you can (intro, conclusion, 4-5 paragraphs each on setting, character etc),memorise and practice adapting those paragraphs to different questions in past papers. Ask your teacher to mark for you. Memorise key set text quotes/themes. Understand what makes a great folio piece.
Chemistry /Physics - create great notes as you go along (look up note taking techniques) and revise, use spaced repetition. Find test questions to practice. Towards end do all available past papers, revise gaps, repeat.
Keep up with the work and revise from the beginning, little and often now 2 x 30-ish mins most week nights (but dont worry if you miss the odd one) , and increase closer to the time and you'll feel less stressed at exam time.
Eat, sleep, exercise well and make sure you have time with friends too.