I do not think practice makes perfect, as often as not, practice at most makes better. There are certain confronting factors that may dictate the effect of your practice in terms of the practice. Accordingly, in any way, you had better use the relevant method to practice before you sit the test.
Good luck to your learning.
I took the test when I left England;
When doin gthe speaking part, try to throw in some idioms or expressions, it really has its impact. There are many books out there that train you to idioms and expression.
To prepare the Writing Part, you can use the "Improve your IELTS : Writing Skils" (Sam McCarter, Mac Millan). It gives you general structures and guides you well on how to go about it, and use elaborate formulas.
That's what I used to supplement my year abroad, and the writing book I recommended was especially helpful.
Good luck :)