Mileil vs Milra

Using a vertical bar (often called a meteg) only on words that are mileil (stress not on the last syllable) following most siddurim including the original Birnbaum, Artscroll, Singers and Koren

Only indicate words that are often mispronounced by using two different symbols, one for mileil and one for milra (stress on the last syllable). This convention is used in Rinat Yisrael

Maybe use a meteg, or other symbol, on every word (except small words with no stress), to indicate the stress, wherever it falls. This is used in Siddur Rav Shabtai Sofer and Siddur Vilna, among others.