Hi there,
I'm in second year of A-levels now and was in near enough the exact same position as you last year. I don't really feel qualified enough to give you tips but hope to inspire you in some way.
I also want to study psychology at uni. I got ABC in AS June exams last year (psychology, maths and biology respectively - biology was 2 marks off the B). This year I'm predicted A*AA and achieved A*A*E in Jan the mocks (psychology, biology and maths respectively - don't ask about maths, just flopped
but always do in assessments, content hasn't sunken in yet!)
I've received offers from all 5 of the universities I've applied to - including Cambridge, UCL and Kings College. My offers range from (A*AA-AAB)
All I can say with Biology is to understand each topic carefully then
do past paper questions from the old spec on them. I didn't do any of this in first year hence the C. The content is largely the same. If you're with OCR, buy the oxford book rather than the pearson one.
Hope this inspires you in some way. All is not lost just keep practising a little everyday, make sure you understand the concepts and answer past exam questions frequently.