Melodic Steps and Leaps
One very old but also very useful rule for melodic writing is that a melodic leap in one direction should be followed by a melodic step in the other direction. Consecutive leaps in the same direction sound very dramatic and have the potential to create a feeling of “the melody falling apart”. On the other hand can extensive stepwise movements feel a little pedestrian.
Of course, there are thousands of melodies that violate that rule and still are highly effective but it is always a nice rule of thumb to follow. Most of the time this rule is not followed in “signature motifs” of melodies but you will hardly find any melody that randomly leaps around. Often consecutive leaps are structured by using specific intervals (e.g. Jurassic Park Island Fanfare) or other structural elements that make the melody accessable. However there are more melodies that follow that rule than those that don’t. The rule mentioned at the beginning has been a strict rule in the baroque era and has become more liberal since then but still, it helps to occasionally remind oneself of it.