Start off with a few domains if you can. You'll get further faster.
If you're a beginner it really is in your best interest to throw a lot out there without fear of failing so you can get a sense of what works and what doesn't work.
You learn from the failures. They are not totally worthless if you gain knowledge you can use in the future.
People often ask me to look at the keyword domains they want to buy and I have to say - most times they are domains I would NOT personally buy.
Does that mean they can't succeed at making money with those domains?
No - it just means that my personal experience leads me to make judgements about the chances of that keyword making money as a web site.
The idea is to find something that works as a web site. It needs to be something you can flesh out and develop when you gain success.
How many articles can you write about a brand or type of a Hair Curler???
I try to find keywords that have lots of related keywords so I can become an authority for that niche.
Now - this is not the place to get into specifics as to how to pick a good keyword that will make you money - as the criteria for picking exact match keyword domains is discussed in great deal in the 12 Step Success Strategy training videos in the Blogging Underground members section.
I would like to say this:
Carefully pick out a good number of them and then before you buy them - look at your list of possible keywords and then based on your GUT along with the fact that they pass the tests I suggest you put them through - pick a few of them.
Not every domain you build will succeed. Not every site that gets traffic will make money.
You need to gain experience and get a feel for what works for you and use that to build a future for yourself.
While my suggestions and strategies are good starting points - you need to take some responsibility yourself and be actively involved in learning how to pick good keyword domains and making money with them.