If you get stuck trying to figure out what numbers to place in a column, row, or square, leave that section and move on to the next segment. Often, once you solve one portion, you can come back to the part that was giving you trouble and see if now you’re able to solve it.
You can also try the strategies above, searching for naked or hidden pairs, and see if that helps. If you’re still stuck, make an educated guess and add a number in the square. Remember which squares you made your guesses with, in case you find out later that there is a mistake and you have to go back and fix it.