Will a Pokemon spawn if I walk without incense?
Pokemon will spawn regardless of whether you walk or not. Unless you're incensed, Pokemon are spawned at locations for everyone rather than for people specifically.
This is the reason that people in rural areas have voiced complaints about the spawn rate for the game.
To answer your question, finding Pokemon is mostly just being in the right place at the right time (even more so since tracking has been reverted to a work-in-progress).