First you look at the title to find out what is the most important word in the title.

Then you read the abstract, keeping in mind that important word that you just found out. You can typically find the novelty of the paper in the abstract section of the paper. Then after than you can read the conclusion section of the paper and you can have a bit more clear idea about what they have really done in their paper.

After you have done this, now you can make the decision that whether this particualr paper is worth your time or not, you can judge this by evaluating on the metric that whether this particular paper is interesting and related to your field or not.

If not then you can skip this paper and move on to the next paper, as you have only so much time and a lot of papers to read.

But if this paper is related to your interets then you can read it in more detail.

then keeping that in mind you have your own thoughts that what this paper can be about, then you find out the exact problem that the authors are trying to solve and by which approach they solve it, that is their novelty.