Are you giving only Group- II or both groups?
In any case, you don't have to fear. There are many ways you can pass, even if you have 1 month in hand and only know few topics in certain subjects.
I can give u some last moment tips, which i followed and cleared, But for Dec exams u have 40+ days, so u can do better.
In OMIS,
For Theory : 1.Take out the scanner (buy it asap if u don't have one)
2. Go through each chapter's questions individually as it is given in the scanner for last 8-10 attempts paper, just give a plain reading to the questions not the answer (theory).
3. From step-2 , you will find that, in each chapter, in the past attempts, certain questions are repeated and while reading you yourself will feel certain questions would seem important. Pick these questions and write it down in a paper chapterwise.
4. This won't take much time but, once you do it, Just study those question thoroughly and learn it.
5. Don't ignore the question which you didn't select. To those questions, give a plain reading atleast once before exam and the questions which you selected read them well.
6. Chapter 2 in OM is too vast and at the same time it is too important and carries a lot of weightage. Still I suggest you, first finish Chapter 1, 3 & 4 and then come to chapter 2. Preferably finish chapter 3 &4 first,then other two. The reason behind it is because these chapters are comparatively small to chapters 1 & 2, and certainly there will be questions asked from these, so why not first secure them?
In Practical :
1. For both OM and IS questions if you don't know from where to solve the practical questions, always follow the institute's book, the questions given there is a prototype on which the exam questions are based.
2. For practical questions you must have conceptual clarity, if you have that, it won't be much difficult to crack them,
3. Do NOT ignore practical questions of IS, yes you heard that right, i said IS. If you take our last attempt paper i.e, June'12, you will know why I am saying this.
This suggestion is only when you hardly have 1 month for exams, didn't complete course even once and don't know what to do, probably not feeling like writing the paper also.
For others who do not fall into this category, if you have 2 months time , then don;t go for such selective study, please study fully.
Hope my Suggestion helps :)