Before you look for subjects, look for backgrounds. Strong graphic elements, bold colours, interesting light, text, architecture. Anything that would make a picture on its own.

Then position yourself so that background is behind whatever walks past. You're not chasing subjects. You're setting a trap.

Watch for: background clutter that competes with your subject. The simpler and stronger the background, the harder it is to take a bad picture when someone walks through it.

The point: the photographers who always seem lucky aren't. They've found a good wall and they're standing in front of it.