I took step 3 in the later part of my 2nd year of residency (even though on paper, the hosp wanted it done in the your first year but my chairman wasn't really pushing the issue).
A friend who went into surg and has some time off between med school and start of residency took it during that time off.
If you are going into a field that's focused on the not so "primary" aspect of healthcare then it's prob better to do it early while things like peds/ob/psych are still fresh in your mind.
I used USMLE world and that was great.
I am not a fan of the "study for 2days protocol". Everyone is diff so def don't short change by not preparing yourself. Better to be overprepped than underprepped.
By no means it is hard like step 1 or step 2, but I had three people who failed (smart people mind you) just because they took the lax attitude that they can just scoot in and scoot out of the exam.
As "easy" as step 3 is, don't embarrass yourself by failing it.
Yes, as EDMD said - don't risk failing it. It's true that it's relatively easy BUT I have an excellent co-resident in my program who came very, very close to actually failing because he subscribed to the whole "number 2 pencil" thing for Step 3. You need to know the content and be somewhat ready to take a 2 day test.