I took the NCLEX 5/30/08 and had 6-8 drug calcs, all requiring some conversions. Know your metric conversions ie: mcg/mg/g/kg, lbs to kgs, and oz's to mls and you should be fine. The 1 thing that sort of freaked me out a bit was having to enter my answers in whole numbers. I hadn't seen this in any study prep. By about my 5th question, I was thinking I had screwed up (instead of entering 12.7 I would enter 13 as my answer based on needing to enter a whole number). I finally got a lengthy ped's drug calc that asked the answer be entered using a decimal. Whew! My last question took at least 7 steps and I had to pay close attention to what it was asking, something like figuring out the total dosage to be given in 24 hours and figuring out the dose to be given each time since it had been ordered TID. Once I settled down, I realized the questions had been getting progressively more difficult which I guess is good.
My advise is to use the system that works best for you. I was taught by a teacher who wrote a book about drug calcs using the "backwards method." Once I learned that, I was fairly comfortable with any question. Good Luck! I'm betting you do well.