if you want get some help from those institutes .But SCJP can be obtained doing some self studies .Here are some tips for a self learner .
First and Foremost
If you are a java professional who has been working with industry based java projects for a long time ,DO NOT underestimate the exam.This exam is looking for a human compiler rather than a good designer.So Take the exam Seriously
Secondly
Become a member of JavaRanch community and be active in SCJP forum .At least read the new threads which are being posted every day.
And thirdly
Buy the SCJP guide by Kathy sierra and Bert Bates.Or if you are a great fan of EBooks go for the ebook.
Fourth Step
Make your Goal .Buy the voucher and fix the exam date. Then your mind will always alert you about the money you are going to miss if you waste time. At least give yourself 2 months for study when you fix the exam date . The exact date will depend on you.If you are new to j2se and can sacrifice 3 good hours in a day for this exam I suggest you to get at least two months for studies.
Fifth step
First read the book one time completely ,doing all the SELF TESTS, going though all the Two Minute Drills ,preparing a good short note for your self.And Code all the examples using a text editor(Notepad++) .Please avoid all those IDEs including Netbeans and Eclipse.And write lot of codes changing the same example in various ways.Spent good 15 minutes with a example which you couldn't answer at first time.