Philodendron hederaceum
Heartleaf philodendron likes soil that is lightly moist but never soggy. It dries out a little faster than you expect in a bright room and a lot slower in a dim one.
Short answer: for a philodendron, with the starting settings below (a 6 inch pot with a drainage hole), check the soil about every 5 to 7 days in spring and summer and every 7 to 11 days in winter, and water when the top inch of soil is dry. Give it a full drink until water runs out the bottom.
Your answer
Water when the soil reaches this point
How it shifts through the year
Check the soil about every 5 to 7 days in spring and summer and water only when the top inch of soil is dry. In winter, growth slows and soil stays wet longer, so expect roughly 7 to 11 days between checks. Always confirm with your finger first.
Water slowly until water runs out the drainage holes, then empty the saucer within an hour. The right amount depends on pot size, so go by drainage and how dry the soil is, not a fixed measure. Avoid light, frequent sips, which only wet the top of the soil.
Check every week or so in warm months, and let the top inch dry before watering. In winter the interval often doubles.
Yellowing across many leaves usually points to wet soil. A few old leaves yellowing slowly is normal.
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Related guides
Estimates use rules of thumb. Always confirm with your finger: push it about an inch into the soil before you water.