my advice: get into brushy places, brush piles with lot of weed and grass around them, brambles. Rabbits like overhead cover and tangles.

Walk through, stopping and starting. Look into the cover. Kick downed limbs and brush. Bunnies like to sit in the limbs and will often flush if you give things a good kick. Be ready to make a quick shot (shotguns are great for this--22s care a real challenge, but are really good if you start looking into cover and spot the rabbit sitting there).

On a side note, a squirrel might present himself or even a quail or pheasant of you're near cropland.