This is what I used for preparation:
O Chem/GChem: I took kaplans course and studied from their study material. They have tons of subject tests but those only touch the surface. Once I had done all the tests from kaplan online review, I then went back to my text books especially for Ochem and Gchem and reviewed topics that I thought were still a little week. Also I used Destroyer for reviewing OChem and GChem and found it really helpful.
Bio: I used Kaplan + Barrons AP bio. I wanted to buy Cliffs but got this one cheap so I used it. I went through it really well since Kaplan is not so much in depth. That is all I used for Bio.
Math: I used CDM and would do 1 test daily. They have 24-25 tests and that is enough for practicing. Also I did tests from MAth Destroyer but did them at my pace without timing as they are considerably harder. That helped BIG time.
PAT: used CDP but did it several times until I was getting 20-21 without making much effort. I stopped counting each of the cubes as I knew just by looking which ones was 2-3 or 4 sided. That saves a lot of time.
English: I used Godfrey RC practice software. They have huge passages but I would take 1 in 30 minutes. That gave me good practice.
I took the Kaplan course for a month but did not spend a lot of time on anything else besides finishing up assigned homework which came up to like 2-3 hours/day. In the last month or so was when I was studying like round the clock. I used to review one science for 3-4 hours, then do a test from MAth destroyer, review it, then do a CDM test to practice for speed and then do a RC or a PAT test every other day and then review the answers.
Practice increasing your speed as time management is the key. I also did like 6 full lengths. I think Achiever tests were great. They were really hard which kept me pushing harder.
Hope this Helps!