I didn't really do this for prelim because ceebs and I didn't really 'study' during it lol
However, how I approach studying in the HSC would still basically apply regardless but yeah
A critical thing is to work out when you work the best and most efficiently. This varies from person to person; I know someone who studies from like 4:30am in the morning and then goes to school (to compensate she sleeps really early). I work incredibly well after 10pm, its just when I get shit done like I'd say I'm atleast 2-3x as productive. Try out different times, and you'll probably notice how much more productive you are at certain times of the day.
Once you've established when you can really hit your groove, you basically rearrange your day around that. I don't really jive with really structured timetable-esque studying (heaps of people do though so whatever works for you), so typically I just do whatever I feel like doing when I feel like doing it. Just make sure that the majority of the time, whatever it is you're doing is legitimately useful to you.
I keep myself honest with a data bar I've created for each of my subjects based on my next big goal. For example with Half-Yearlies coming up, I have a bar for each subject illustrating the percentage I feel I'm ready for that Half-Yearly assessment, with 100% being I'm ready to obliterate the exam. By doing this, I can see whether I'm lagging in something and pull it up.
Now, I like to think of time as a resource. You need to distribute it in such a way that is most effective for you in meeting whatever you're goals are. For example, you need to sleep sufficient hours, you need to allocate time to just chill otherwise you will explode. Think of it as an investment in yourself. You need time to study, and any other commitments you might have.
You said that you are really tired after you come home from school - so am I. So generally speaking, if I feel that I'm not going to be very productive if I try and work now, I invest the time somewhere I will get a better return; namely sleep. This works well for me, because if I nap for 2-3 hours when I get home, I can stay up later without it really effecting how I feel or perform. This means that I can spend a longer time working in my 'zone' time after 10pm, and so I get more done.
Basically, just make use of your time however it is best spent. This requires responsibility and maturity on your part - you need to hold yourself accountable. If that means sleep then sleep. If that means homework, then do homework. Keep in mind that it would be prudent not to waste the time when you are best working on something menial like basic mathematics. It's still important practice, but you don't need your 100% to do it. Instead do past papers, or difficult questions, or writing notes and understanding conceptual information.
If you need that structured time distribution to work efficiently, then I would recommend a study time table, something like WrittenLoveLetters's would be very effective imo
Yes I do follow it.
Yes there are times where dinner and family stuff disrupt it - I just merely find the time I'm at and continue from there.