I'll admit the question was probably too vague and I should have clarified it more... Mm, my goal for next year would be to achieve an 88 ATAR. I want to study Commerce at Melbourne but I'm considering science as well. 
Haha that's all good, now we can accurately give you an answer!
88 is definitely achievable, but you will need to work for it. What others have said is very true, but I believe that achieving over 95 is about hard work and intelligence, but if you aren't, say "intellectually gifted", up to 90 I think should be fairly achievable for the average student given hard work. I like this quote- "aim high in case you fall short". This encourages you to work hard, set your sights on something that may be out of reach, but not completely unattainable. Don't say I want a 99.95 for no particular reason. Say okay, I want a 92 to push myself and encourage myself to work harder. If you achieve it, great, well done! If you don't, there's still that buffer of 4 atar points ish I don't know what they are called haha, which can definitely still be in your range.
It becomes easier to succeed in vce (as you defined as getting the atar to your course), if you set your sights on something higher that is not so make it or break it. Achieving a personal goal that will better you no matter the margin, such as working harder, is less daunting than achieving career or education goals, such as needing entry to a course to have a career and get a job in life, you see what I mean? So set your goals higher than what you need, and even if you don't achieve your personal goals, it's still likely that you achieve your educational ones, and you have all of university to complete your personal goals, as well as the rest of your life!

88 is achievable, but it depends slightly on your subjects. What are you good at- English, humanities, maths, science? Are you taking subjects based on your strengths and career goals? Are you doing well in those subjects? Are you doing all you can to maximise your potential? Can you do more to increase your chances of succeeding at the end of next year?
These are the questions you must ask yourself. Analyse your situation and understand what you are doing and what more you can do to make your goals more achievable and in reach. Are you distracted in class, do you not understand content, do you need to practice application more, do you need help from teachers or a tutor? Find out how to help yourself. Even having a chat to your teachers is helpful. You don't need to see a biology teacher and say I ddon't understand osmosis in plant cells. See them and say look I'm not too happy with where I'm at, what would you recommend that I can do to improve? Most teachers would be delighted to direct you to wherever you need to go.
After identifying your weaknesses all it is is hard work. Fix your weaknesses, do the set work, do extra work. Learn, ask questions, teach others. Read, study, answer questions. Do practice exams. This will ensure you solidify your knowledge throughout the year so come exam time you don't need to rote learn everything again, its in your head already and you can just practice. Then smash those exams, watch your atar come in and smile because you've got over the 88 you needed!
In short, if you aren't doing the best you can now, all you need to do is identify your weaknesses, because vce, as mentioned by another member, doesn't reward intelligence. Then find ways to fix them and work for what you want, and if you can do that then you will definitely succeed, both in vce and in life.
Best of luck and I'm sure you're going to do well!
