If there is a question that interests you, have a look at that, if not choose the topic you are most familiar with in terms of the content and the possible debates around the area.
Identify the main points of the question, what is it asking, what topic do you have to focus on?
Focus your research and reading around the specific topic, and see what other authors have to say about it. It is also important from here to decide whether you agree or disagree with them.
Dive straight into the body of the essay if you find it easier to do so. You can then return to the introduction later on.
Sometimes I would feel like putting off coursework for later, but it is important to start early and motivate yourself. Coursework, compared to seminar preparation are often more important as they count towards your final grade. So make sure to keep up your effort towards assignment periods.
If you can, talk to your academic advisor or tutor as they may be able to guide you in the right direction when it comes to choosing essay questions. Or, you can always ask them if the question you have chosen is right.
Once you know what the question is about, skip the introduction. I always find introductions so hard to write and if you just go in with your first point, it can get your ideas flowing and then you can come back to the introduction later.
Write out a plan. This always helps me as it gives me some sort of structure to the work and I can jot down ideas for each point as I go along if I think of one which really helps later.
Start early! If you can, try and start a couple of weeks in advance so that if one day you really can't think of anything, you still have plenty of time to write it. Sometimes, leaving it until the last minute makes me feel stressed and unable to think of good ideas.
Lastly, if you are struggling to think of ideas, you could always ask friends or family if they know anything you could write about. It doesn't hurt to ask around, as long as you don't copy anything and this may just make you think of an idea. You never know!