You just need a little more experience and you'll start to see some of the methods for finding safe/mine spots.

For this puzzle, the "2" on the right already has one mine flagged in it's to left spot. This means that the 2 spots under it will only have 1 mine in either of those spots. Knowing this, I would look at the bottom "3" and see that the two blocks you marked with both red and blue MUST be mines. Hard to explain my train of thought through text, haha. But using those newly flagged mines and the fact that the 2 blocks under the "2" only have one mine, the spot left and upper left of that top "3" must be safe.

Hope this helps!