When I was at my lowest I dreamed of hobomaxing and riding the rails so I spent a lot of time walking along train tracks and exploring the buildings that are around them.
Most of my urbex now is related to going a low as possible and going up as high as possible. I enjoy lifting up grates/manhole covers and exploring(I have yet to wade through any smelly sewage, but I am prepared for it). I like scaling water towers, but I'm thinking out giving a wind turbine a climb eventually.

For finding abandoned buildings just cruise around to areas that you know are low income. I live in a once booming town in the rust-belt so finding old buildings is pretty easy. If you live in a newer development head towards the outskirts of an older city and you should be able to some urbex opportunities. Keep in mind to where you can park without being questioned or better yet bike(easy to conceal) or the best option walk there. Use google maps for both aerial views and street views(make sure you have most recent pics otherwise it can be quite the surprise finding that the building was demolished by the time you get there).
Also, don't limit your urbex to just abandoned places learn some infiltration skills and explore the subsystems of active buildings(the world is more security conscious now, but learning the basics of social engineering is invaluable).
If you do come across hoboes in your ventures just remember you are on their turf. I became friendly with a hobo in an area I would frequent, some are just out of their mind and can be pretty dangerous. Usually if I see fresh evidence of someone living there I'll leave immediately as to not disturb them.
But like with gun safety the number one rule is to have fun :^)