Hi!
First of all let me tell you that I am not an IITian but am preparing for 2005-JEE. This might not exactly be a success mantra but its a first hand account of things I find imperative.
Numero Uno-
First and foremost U need to be motivated. Forced hard-work might work in Xth & XIIth but surely not in IIT-JEE. How to get motivated? Find Ur mantra Urself - I for one read IIT-JEE reviews on Mouthshut every week to get pumped up (sounds silly?...it isnt). U may talk to studious friends or teachers or parents, whatever works for U is just fine.
Books-
Read the standard recommended books but make sure U dont get into too many books simultaneously. Be a touch selective here.
Planning-
Plan Ur studies - easier said than done. Make daily and weekly targets according to Ur plan as to when U want to complete the course material and start doing mock papers. Ideally leave 3-4 months for paper solving.
Miscellaneous points-
Be absolutely thorough with concepts. Dont move forward unless U feel Uve got it perfectly right. Take help in this regard from teachers.
Solve lots (and I mean LOTS) of papers in exam conditions. A lot of aspirants dont find this important and then face problems like leaving solvable (by them) questions and unfamiliarity with the pattern.
Dont neglect Ur strengths. Work on Ur weaknesses alright but prepare some topics in each subject so well that U can solve almost any question from them.
Revision is indispensable, considering the large syllabus. Make sure U revise every topic sufficiently.
Coaching-
Controversial topic this. I personally am not taking coaching apart from Brilliants correspondence course ( but thats more of a compulsion than a choice as theres no good coaching centre anywhere near I live). I belive If U have access to a good institute, then do go in for coaching but many aspirants succeed without coaching as well. But, It requires meticulous planning and a hell lot of hard work.
Trend of JEE-
JEE is surely changing - Physics is getting a touch easier and maths tougher. This is easy to notice in last few years papers. And yes, Mechanics is no longer half the physics paper. Give special attention to important topics like Calculus, Co-Ordinate Geometry, Organic Chem., Modern Physics etc.
Lastly-
Forget TV, Cricket, Hanging out etc. until the paper. Trust me, Its worth it. Have faith in Urself. Negative thoughts will cross Ur mind but dont heed to them. And yes-
BEST OF LUCK!