I've had a few interviews before and they've all been very casual. They always ask me about my previous experience. Most importantly, don't be too focused on the technical stuff such as listing your achievements and what you can do. Mention them of course, but since you'll be someone's assistant and you'll probably be working alongside them, that someone is generally looking for an assistant that they can get along with. So be natural and confident. Oh and ALWAYS have questions prepared. Not just basic stuff like what are my responsibilities, go on their lab's website and figure out questions based on their research!

Applied online and heard back over a month later. 2 full time research engineers interviewed me in a typical interview setting. General STAR questions and the usual why do you want to work here. Couple technical and hands on questions/problem solving that was on the trickier side.