Software engineer interview at any of these companies are quite standard and general, you can expect to have the similar kind of interviews as other big companies like Amazon, Facebook, etc... Various skills are evaluated including general technical skill (data structure/algorithm), system design, testing, communication, analysis ability etc. and since the whole process is quite standard, certain ways of preparation can definitely make your life easier. What you need to prepare is the case by case and I'll try to give some general tips, which you should always try to adjust to make them work for you.
STEP 1: DATA STRUCTURE AND ALGORITHMS PREPARATION
I would assume you already finish those basic courses at school so that you are not learning everything from scratch. Then this process may take one to several months. The reason you should prepare well for data structure and algorithms first is that they are really the foundation of most software engineer interviews. A real interview question is like asking you to solve a problem with the combination of skills you learned from these basic knowledge, also you should be quite fast when analyzing time/space complexity, which is covered in this book as well.
STEP 2: BE FAMILIAR WITH GENERAL CODING QUESTIONS
At this step, you should be quite familiar with basic knowledge and concepts of computer science, it's better to practice with some real coding questions. This may take several months as well depending on your time and how familiar you are with data structure and algorithms. The idea of this step is to teach you how to use what you learned from those books to solve a real question and give you some ideas about what kind of questions is asked in a general interview. In fact I don't have much suggestion in this step instead of delving into those questions and practice as much as you can.
STEP 3: SEARCH REAL QUESTIONS FROM THE COMPANY
Suppose you are preparing interviews for Facebook, then I'd suggest you do some Google search and it won't be hard for you to get tons of questions from Facebook interviews. Since the different company has different styles and focuses, this approach will help you be more familiar and prepared for that company's interview. Don't try to memorize questions and answers as these companies usually avoid asking questions leaked on public, so it's quite unlikely to encounter the same question again.
STEP 4: KEEP PRACTICING
At this step, I expect you to have maybe 1 month left and you should be equipped with all you need for an interview except for experiences. The technical interview doesn't only evaluate your coding ability, but a variety of skills and abilities like communication skills, analysis ability etc... Also, many people will feel nervous solving a problem when someone is looking over his shoulder, thus he may even fail in the simplest questions. I'd suggest you to find a friend who is also preparing for an interview, you guys can conduct mock interviews with each other and try to be familiar with this kind of intense atmosphere.
Conclusion:
It's highly recommended to make a preparation timeline and stick to it. Also spending half-hour a day on preparation won't work normally. There's no better way than keep practicing and eventually you're going to crack the interview.
