Well, it's been a while since I finished IPT, so...I'm guessing you're asking for general studying advice? What I did was constant over the year and so can't really be replicated two days before the exam.
But. If you have the Heinemann text book? That's not enough, in terms of detail. It's great for last minute study and making sure that you've got the concepts down, but to get better marks you'll need a more detailed textbook. My school provided me with the Sam Davis textbook - which was
way too detailed. That said, its level of detail was excellent - it's just that a lot of it was irrelevant, e.g. compression algorithms explained, such as Hoffman and run-length. Evidently it'll be too late now if you don't have a detailed textbook - I'm not sure what the others are like.
Know your concepts. Comb through the syllabus and make sure you're comfortable with each point. It's quite a detailed syllabus, which is great, you'll know what to target - if you go through that and feel good, then great, that's a good sign
Make sure to do multiple choice questions online/past papers. But remember that the syllabus is your best friend.