1) When you're ready to lie down, simply rest your feet on the lap of the seat poacher.

2) Cough aggressively without covering your mouth directly towards the seat poacher, if possible, do this while holding eye contact.

3) If seat poacher has taken the aisle seat and you're left in the window, get up to use the lav constantly.

4) Engage in a lengthy conversation with the seat poacher about a very personal/awkward/controversial topic until they are so uncomfortable they must leave.