The first place to begin with trying to construct a simile is to consider the quality or behavior you are attempting to figuratively represent and figure out something else that has that quality or engages in that behavior. Also, since we are supposed to support Odysseus, Telemachus, and Penelope in their loyalty and steadfastness and bravery, you'll want to form comparisons that are relatively positive in connotation.
So, if your first simile should address Odysseus's skills in planning schemes, you might consider some other creature that is really skillful at planning. One that comes to mind for me is a spider. A spider seems to plan and create an intricate web with such ease; further, webs are incredibly strong and enable the spider's survival, just as his schemes are. A spider seems like an excellent creature to serve as a comparison for Odysseus's skill in planning schemes.
Next, Penelope is patient and resourceful, so try to consider a creature that also has these qualities. Perhaps a bird? Birds make their homes from found items, and mother birds sit on their eggs, patiently waiting for them to hatch. Penelope is likewise resourceful when protecting her home and family and is quite patient while waiting for her husband to return.
Likewise, think of a creature that is considered to be brave, as Telemachus is, and begin there. Because Odysseus is compared to a lion via an epic simile in the text already, you might entertain the idea of comparing Telemachus to a lion cub, a younger animal who is nonetheless brave enough to take on other, full-grown animals (who would be the suitors in this simile).