There are sample ballots that can be downloaded from COMELEC's official site. COMELEC advises that we download it and practice with the shading thingy. As a matter of fact, practicing can help. Shading is an important factor. Validity of your vote will depend on how you shade those ovals beside a candidate's name. No stray marks on the ballot is allowed. Another important thing is the number of ovals you have to shade in a section. For the President, you must choose only one candidate, and shade that candidate's oval. The same goes with the Vice-President. For Senators, you have to choose 12, and for the Party List, you choose only 1.
For more information, you may visit