This chart makes it easier to work from the bottom up. The lower row on this chart is row one. The row directly above it is row two, and so on.
After you've crocheted a row, compare it with the row above it on the chart. If there are fewer stitches on the row above, you'll need to decrease. If there are the same amount of stitches, you don't need to decrease.
Starting with row 3, I found it easiest to split the heart in halves and only work half at a time.
After you've completed this chart, you're going to flip your crocheted piece upside-down and start working the next chart.
Or, if you'd prefer, you can work from the free heart motif pattern, which includes written instructions for the crochet work.