I personally find studying alone to be the best method for me.
The few times I have studied in a group, it's led to plenty of distractions, and, in the end, we never end up studying for anything.
The study habits that work best for me would have to include studying in a very quiet place, preferably in my house when I'm the only one in the house. I like to be able to talk out what I'm studying over and over without having to bother others or embarrass myself for talking to myself, haha. I never, ever, ever (Taylor Swift) leave anything to study for last minute. Cramming for me is a big no-no. I start studying from the first day of receiving the material until the day before the test.